diff --git a/src/index-bar/index.js b/src/index-bar/index.js
index b6954f830..38977318c 100644
--- a/src/index-bar/index.js
+++ b/src/index-bar/index.js
@@ -17,7 +17,7 @@ export default createComponent({
   mixins: [
     TouchMixin,
     ParentMixin('vanIndexBar'),
-    BindEventMixin(function(bind) {
+    BindEventMixin(function (bind) {
       if (!this.scroller) {
         this.scroller = getScrollEventTarget(this.$el);
       }
@@ -84,16 +84,11 @@ export default createComponent({
 
   methods: {
     onScroll() {
-      let scrollTop;
-      if (this.scroller === window || this.scroller === document.body) {
-        scrollTop = getScrollTop(this.scroller);
-      } else {
-        // see: https://github.com/youzan/vant/issues/3774
-        scrollTop = 0;
-      }
+      const scrollTop = getScrollTop(this.scroller);
+      const scrollerRect = this.getScrollerRect();
       const rects = this.children.map(item => ({
         height: item.height,
-        top: getElementTop(item.$el)
+        top: this.getElementTop(item.$el, scrollerRect)
       }));
 
       const active = this.getActiveAnchorIndex(scrollTop, rects);
@@ -104,11 +99,11 @@ export default createComponent({
         this.children.forEach((item, index) => {
           if (index === active) {
             item.active = true;
-            item.top = Math.max(this.stickyOffsetTop, rects[index].top - scrollTop);
+            item.top = Math.max(this.stickyOffsetTop, rects[index].top - scrollTop) + scrollerRect.top;
           } else if (index === active - 1) {
             const activeItemTop = rects[active].top - scrollTop;
             item.active = activeItemTop > 0;
-            item.top = activeItemTop - item.height;
+            item.top = activeItemTop + scrollerRect.top - item.height;
           } else {
             item.active = false;
           }
@@ -116,6 +111,32 @@ export default createComponent({
       }
     },
 
+    getScrollerRect() {
+      const { scroller } = this;
+      let scrollerRect = {
+        top: 0,
+        left: 0,
+      };
+
+      if (scroller.getBoundingClientRect) {
+        scrollerRect = scroller.getBoundingClientRect();
+      }
+
+      return scrollerRect;
+    },
+
+    getElementTop(ele, scrollerRect) {
+      const { scroller } = this;
+
+      if (scroller === window || scroller === document.body) {
+        return getElementTop(ele);
+      }
+
+      const eleRect = ele.getBoundingClientRect();
+
+      return eleRect.top - scrollerRect.top + getScrollTop(scroller);
+    },
+
     getActiveAnchorIndex(scrollTop, rects) {
       for (let i = this.children.length - 1; i >= 0; i--) {
         const prevHeight = i > 0 ? rects[i - 1].height : 0;
@@ -196,7 +217,7 @@ export default createComponent({
       <div class={bem()}>
         <div
           class={bem('sidebar')}
-          style={{ zIndex: this.zIndex }}
+          style={{ zIndex: this.zIndex + 1 }}
           onClick={this.onClick}
           onTouchstart={this.touchStart}
           onTouchmove={this.onTouchMove}
diff --git a/src/index-bar/test/__snapshots__/demo.spec.js.snap b/src/index-bar/test/__snapshots__/demo.spec.js.snap
index 1bdc3d5c2..5f19d843e 100644
--- a/src/index-bar/test/__snapshots__/demo.spec.js.snap
+++ b/src/index-bar/test/__snapshots__/demo.spec.js.snap
@@ -13,7 +13,7 @@ exports[`renders demo correctly 1`] = `
     <div class="van-tabs__content">
       <div role="tabpanel" class="van-tab__pane" style="">
         <div class="van-index-bar">
-          <div class="van-index-bar__sidebar" style="z-index: 1;"><span data-index="A" class="van-index-bar__index">A</span><span data-index="B" class="van-index-bar__index">B</span><span data-index="C" class="van-index-bar__index">C</span><span data-index="D" class="van-index-bar__index">D</span><span data-index="E" class="van-index-bar__index">E</span><span data-index="F" class="van-index-bar__index">F</span><span data-index="G" class="van-index-bar__index">G</span><span data-index="H" class="van-index-bar__index">H</span><span data-index="I" class="van-index-bar__index">I</span><span data-index="J" class="van-index-bar__index">J</span><span data-index="K" class="van-index-bar__index">K</span><span data-index="L" class="van-index-bar__index">L</span><span data-index="M" class="van-index-bar__index">M</span><span data-index="N" class="van-index-bar__index">N</span><span data-index="O" class="van-index-bar__index">O</span><span data-index="P" class="van-index-bar__index">P</span><span data-index="Q" class="van-index-bar__index">Q</span><span data-index="R" class="van-index-bar__index">R</span><span data-index="S" class="van-index-bar__index">S</span><span data-index="T" class="van-index-bar__index">T</span><span data-index="U" class="van-index-bar__index">U</span><span data-index="V" class="van-index-bar__index">V</span><span data-index="W" class="van-index-bar__index">W</span><span data-index="X" class="van-index-bar__index">X</span><span data-index="Y" class="van-index-bar__index">Y</span><span data-index="Z" class="van-index-bar__index">Z</span></div>
+          <div class="van-index-bar__sidebar" style="z-index: 2;"><span data-index="A" class="van-index-bar__index">A</span><span data-index="B" class="van-index-bar__index">B</span><span data-index="C" class="van-index-bar__index">C</span><span data-index="D" class="van-index-bar__index">D</span><span data-index="E" class="van-index-bar__index">E</span><span data-index="F" class="van-index-bar__index">F</span><span data-index="G" class="van-index-bar__index">G</span><span data-index="H" class="van-index-bar__index">H</span><span data-index="I" class="van-index-bar__index">I</span><span data-index="J" class="van-index-bar__index">J</span><span data-index="K" class="van-index-bar__index">K</span><span data-index="L" class="van-index-bar__index">L</span><span data-index="M" class="van-index-bar__index">M</span><span data-index="N" class="van-index-bar__index">N</span><span data-index="O" class="van-index-bar__index">O</span><span data-index="P" class="van-index-bar__index">P</span><span data-index="Q" class="van-index-bar__index">Q</span><span data-index="R" class="van-index-bar__index">R</span><span data-index="S" class="van-index-bar__index">S</span><span data-index="T" class="van-index-bar__index">T</span><span data-index="U" class="van-index-bar__index">U</span><span data-index="V" class="van-index-bar__index">V</span><span data-index="W" class="van-index-bar__index">W</span><span data-index="X" class="van-index-bar__index">X</span><span data-index="Y" class="van-index-bar__index">Y</span><span data-index="Z" class="van-index-bar__index">Z</span></div>
           <div>
             <div>
               <div class="van-index-anchor">A</div>
diff --git a/src/index-bar/test/__snapshots__/index.spec.js.snap b/src/index-bar/test/__snapshots__/index.spec.js.snap
index bef60e616..f8d487743 100644
--- a/src/index-bar/test/__snapshots__/index.spec.js.snap
+++ b/src/index-bar/test/__snapshots__/index.spec.js.snap
@@ -2,7 +2,7 @@
 
 exports[`custom anchor text 1`] = `
 <div class="van-index-bar">
-  <div class="van-index-bar__sidebar" style="z-index: 1;"><span data-index="A" class="van-index-bar__index">A</span><span data-index="B" class="van-index-bar__index">B</span><span data-index="C" class="van-index-bar__index">C</span><span data-index="D" class="van-index-bar__index">D</span><span data-index="E" class="van-index-bar__index">E</span><span data-index="F" class="van-index-bar__index">F</span><span data-index="G" class="van-index-bar__index">G</span><span data-index="H" class="van-index-bar__index">H</span><span data-index="I" class="van-index-bar__index">I</span><span data-index="J" class="van-index-bar__index">J</span><span data-index="K" class="van-index-bar__index">K</span><span data-index="L" class="van-index-bar__index">L</span><span data-index="M" class="van-index-bar__index">M</span><span data-index="N" class="van-index-bar__index">N</span><span data-index="O" class="van-index-bar__index">O</span><span data-index="P" class="van-index-bar__index">P</span><span data-index="Q" class="van-index-bar__index">Q</span><span data-index="R" class="van-index-bar__index">R</span><span data-index="S" class="van-index-bar__index">S</span><span data-index="T" class="van-index-bar__index">T</span><span data-index="U" class="van-index-bar__index">U</span><span data-index="V" class="van-index-bar__index">V</span><span data-index="W" class="van-index-bar__index">W</span><span data-index="X" class="van-index-bar__index">X</span><span data-index="Y" class="van-index-bar__index">Y</span><span data-index="Z" class="van-index-bar__index">Z</span></div>
+  <div class="van-index-bar__sidebar" style="z-index: 2;"><span data-index="A" class="van-index-bar__index">A</span><span data-index="B" class="van-index-bar__index">B</span><span data-index="C" class="van-index-bar__index">C</span><span data-index="D" class="van-index-bar__index">D</span><span data-index="E" class="van-index-bar__index">E</span><span data-index="F" class="van-index-bar__index">F</span><span data-index="G" class="van-index-bar__index">G</span><span data-index="H" class="van-index-bar__index">H</span><span data-index="I" class="van-index-bar__index">I</span><span data-index="J" class="van-index-bar__index">J</span><span data-index="K" class="van-index-bar__index">K</span><span data-index="L" class="van-index-bar__index">L</span><span data-index="M" class="van-index-bar__index">M</span><span data-index="N" class="van-index-bar__index">N</span><span data-index="O" class="van-index-bar__index">O</span><span data-index="P" class="van-index-bar__index">P</span><span data-index="Q" class="van-index-bar__index">Q</span><span data-index="R" class="van-index-bar__index">R</span><span data-index="S" class="van-index-bar__index">S</span><span data-index="T" class="van-index-bar__index">T</span><span data-index="U" class="van-index-bar__index">U</span><span data-index="V" class="van-index-bar__index">V</span><span data-index="W" class="van-index-bar__index">W</span><span data-index="X" class="van-index-bar__index">X</span><span data-index="Y" class="van-index-bar__index">Y</span><span data-index="Z" class="van-index-bar__index">Z</span></div>
   <div>
     <div class="van-index-anchor">Title A</div>
   </div>
@@ -14,7 +14,7 @@ exports[`custom anchor text 1`] = `
 
 exports[`scroll and update active anchor 1`] = `
 <div class="van-index-bar">
-  <div class="van-index-bar__sidebar" style="z-index: 1;"><span data-index="A" class="van-index-bar__index">A</span><span data-index="B" class="van-index-bar__index van-index-bar__index--active" style="color: rgb(7, 193, 96);">B</span><span data-index="C" class="van-index-bar__index">C</span><span data-index="D" class="van-index-bar__index">D</span><span data-index="E" class="van-index-bar__index">E</span><span data-index="F" class="van-index-bar__index">F</span><span data-index="G" class="van-index-bar__index">G</span><span data-index="H" class="van-index-bar__index">H</span><span data-index="I" class="van-index-bar__index">I</span><span data-index="J" class="van-index-bar__index">J</span><span data-index="K" class="van-index-bar__index">K</span><span data-index="L" class="van-index-bar__index">L</span><span data-index="M" class="van-index-bar__index">M</span><span data-index="N" class="van-index-bar__index">N</span><span data-index="O" class="van-index-bar__index">O</span><span data-index="P" class="van-index-bar__index">P</span><span data-index="Q" class="van-index-bar__index">Q</span><span data-index="R" class="van-index-bar__index">R</span><span data-index="S" class="van-index-bar__index">S</span><span data-index="T" class="van-index-bar__index">T</span><span data-index="U" class="van-index-bar__index">U</span><span data-index="V" class="van-index-bar__index">V</span><span data-index="W" class="van-index-bar__index">W</span><span data-index="X" class="van-index-bar__index">X</span><span data-index="Y" class="van-index-bar__index">Y</span><span data-index="Z" class="van-index-bar__index">Z</span></div>
+  <div class="van-index-bar__sidebar" style="z-index: 2;"><span data-index="A" class="van-index-bar__index">A</span><span data-index="B" class="van-index-bar__index van-index-bar__index--active" style="color: rgb(7, 193, 96);">B</span><span data-index="C" class="van-index-bar__index">C</span><span data-index="D" class="van-index-bar__index">D</span><span data-index="E" class="van-index-bar__index">E</span><span data-index="F" class="van-index-bar__index">F</span><span data-index="G" class="van-index-bar__index">G</span><span data-index="H" class="van-index-bar__index">H</span><span data-index="I" class="van-index-bar__index">I</span><span data-index="J" class="van-index-bar__index">J</span><span data-index="K" class="van-index-bar__index">K</span><span data-index="L" class="van-index-bar__index">L</span><span data-index="M" class="van-index-bar__index">M</span><span data-index="N" class="van-index-bar__index">N</span><span data-index="O" class="van-index-bar__index">O</span><span data-index="P" class="van-index-bar__index">P</span><span data-index="Q" class="van-index-bar__index">Q</span><span data-index="R" class="van-index-bar__index">R</span><span data-index="S" class="van-index-bar__index">S</span><span data-index="T" class="van-index-bar__index">T</span><span data-index="U" class="van-index-bar__index">U</span><span data-index="V" class="van-index-bar__index">V</span><span data-index="W" class="van-index-bar__index">W</span><span data-index="X" class="van-index-bar__index">X</span><span data-index="Y" class="van-index-bar__index">Y</span><span data-index="Z" class="van-index-bar__index">Z</span></div>
   <div data-index="0">
     <div class="van-index-anchor">1</div>
   </div>
@@ -32,7 +32,7 @@ exports[`scroll and update active anchor 1`] = `
 
 exports[`scroll and update active anchor 2`] = `
 <div class="van-index-bar">
-  <div class="van-index-bar__sidebar" style="z-index: 1;"><span data-index="A" class="van-index-bar__index">A</span><span data-index="B" class="van-index-bar__index van-index-bar__index--active" style="color: rgb(7, 193, 96);">B</span><span data-index="C" class="van-index-bar__index">C</span><span data-index="D" class="van-index-bar__index">D</span><span data-index="E" class="van-index-bar__index">E</span><span data-index="F" class="van-index-bar__index">F</span><span data-index="G" class="van-index-bar__index">G</span><span data-index="H" class="van-index-bar__index">H</span><span data-index="I" class="van-index-bar__index">I</span><span data-index="J" class="van-index-bar__index">J</span><span data-index="K" class="van-index-bar__index">K</span><span data-index="L" class="van-index-bar__index">L</span><span data-index="M" class="van-index-bar__index">M</span><span data-index="N" class="van-index-bar__index">N</span><span data-index="O" class="van-index-bar__index">O</span><span data-index="P" class="van-index-bar__index">P</span><span data-index="Q" class="van-index-bar__index">Q</span><span data-index="R" class="van-index-bar__index">R</span><span data-index="S" class="van-index-bar__index">S</span><span data-index="T" class="van-index-bar__index">T</span><span data-index="U" class="van-index-bar__index">U</span><span data-index="V" class="van-index-bar__index">V</span><span data-index="W" class="van-index-bar__index">W</span><span data-index="X" class="van-index-bar__index">X</span><span data-index="Y" class="van-index-bar__index">Y</span><span data-index="Z" class="van-index-bar__index">Z</span></div>
+  <div class="van-index-bar__sidebar" style="z-index: 2;"><span data-index="A" class="van-index-bar__index">A</span><span data-index="B" class="van-index-bar__index van-index-bar__index--active" style="color: rgb(7, 193, 96);">B</span><span data-index="C" class="van-index-bar__index">C</span><span data-index="D" class="van-index-bar__index">D</span><span data-index="E" class="van-index-bar__index">E</span><span data-index="F" class="van-index-bar__index">F</span><span data-index="G" class="van-index-bar__index">G</span><span data-index="H" class="van-index-bar__index">H</span><span data-index="I" class="van-index-bar__index">I</span><span data-index="J" class="van-index-bar__index">J</span><span data-index="K" class="van-index-bar__index">K</span><span data-index="L" class="van-index-bar__index">L</span><span data-index="M" class="van-index-bar__index">M</span><span data-index="N" class="van-index-bar__index">N</span><span data-index="O" class="van-index-bar__index">O</span><span data-index="P" class="van-index-bar__index">P</span><span data-index="Q" class="van-index-bar__index">Q</span><span data-index="R" class="van-index-bar__index">R</span><span data-index="S" class="van-index-bar__index">S</span><span data-index="T" class="van-index-bar__index">T</span><span data-index="U" class="van-index-bar__index">U</span><span data-index="V" class="van-index-bar__index">V</span><span data-index="W" class="van-index-bar__index">W</span><span data-index="X" class="van-index-bar__index">X</span><span data-index="Y" class="van-index-bar__index">Y</span><span data-index="Z" class="van-index-bar__index">Z</span></div>
   <div data-index="0" style="height: 10px;">
     <div class="van-index-anchor van-index-anchor--sticky van-hairline--bottom" style="transform: translate3d(0, 0px, 0); color: rgb(7, 193, 96); z-index: 1;">1</div>
   </div>