diff --git a/src/collapse-item/index.js b/src/collapse-item/index.tsx
similarity index 81%
rename from src/collapse-item/index.js
rename to src/collapse-item/index.tsx
index 3f7ce995d..7181ab08b 100644
--- a/src/collapse-item/index.js
+++ b/src/collapse-item/index.tsx
@@ -10,7 +10,7 @@ import { useLazyRender } from '../composables/use-lazy-render';
 
 // Components
 import Cell, { cellProps } from '../cell';
-import { COLLAPSE_KEY } from '../collapse';
+import { COLLAPSE_KEY, CollapseProvide } from '../collapse';
 
 const [createComponent, bem] = createNamespace('collapse-item');
 
@@ -26,18 +26,21 @@ export default createComponent({
   },
 
   setup(props, { slots }) {
-    const wrapperRef = ref();
-    const contentRef = ref();
-    const { parent, index } = useParent(COLLAPSE_KEY);
+    const wrapperRef = ref<HTMLElement>();
+    const contentRef = ref<HTMLElement>();
+    const { parent, index } = useParent<CollapseProvide>(COLLAPSE_KEY);
+
+    if (!parent) {
+      if (process.env.NODE_ENV !== 'production') {
+        console.error(
+          '[Vant] CollapseItem must be a child component of Collapse.'
+        );
+      }
+      return;
+    }
 
     const currentName = computed(() => props.name ?? index.value);
-
-    const expanded = computed(() => {
-      if (parent) {
-        return parent.isExpanded(currentName.value);
-      }
-      return null;
-    });
+    const expanded = computed(() => parent.isExpanded(currentName.value));
 
     const show = ref(expanded.value);
     const lazyRender = useLazyRender(show);
@@ -46,7 +49,7 @@ export default createComponent({
       if (!expanded.value) {
         show.value = false;
       } else {
-        wrapperRef.value.style.height = '';
+        wrapperRef.value!.style.height = '';
       }
     };
 
@@ -71,11 +74,11 @@ export default createComponent({
         const { offsetHeight } = contentRef.value;
         if (offsetHeight) {
           const contentHeight = `${offsetHeight}px`;
-          wrapperRef.value.style.height = value ? 0 : contentHeight;
+          wrapperRef.value.style.height = value ? '0' : contentHeight;
 
           // use double raf to ensure animation can start
           doubleRaf(() => {
-            wrapperRef.value.style.height = value ? contentHeight : 0;
+            wrapperRef.value!.style.height = value ? contentHeight : '0';
           });
         } else {
           onTransitionEnd();
diff --git a/src/collapse/index.js b/src/collapse/index.tsx
similarity index 60%
rename from src/collapse/index.js
rename to src/collapse/index.tsx
index 00b23b879..2bf967406 100644
--- a/src/collapse/index.js
+++ b/src/collapse/index.tsx
@@ -1,3 +1,4 @@
+import { PropType } from 'vue';
 import { createNamespace } from '../utils';
 import { BORDER_TOP_BOTTOM } from '../utils/constant';
 import { useChildren } from '@vant/use';
@@ -6,10 +7,20 @@ const [createComponent, bem] = createNamespace('collapse');
 
 export const COLLAPSE_KEY = 'vanCollapse';
 
+export type CollapseProvide = {
+  toggle: (name: number | string, expanded: boolean) => void;
+  isExpanded: (name: number | string) => boolean;
+};
+
 export default createComponent({
   props: {
     accordion: Boolean,
-    modelValue: [String, Number, Array],
+    modelValue: {
+      type: [String, Number, Array] as PropType<
+        string | number | Array<string | number>
+      >,
+      required: true,
+    },
     border: {
       type: Boolean,
       default: true,
@@ -21,24 +32,28 @@ export default createComponent({
   setup(props, { emit, slots }) {
     const { linkChildren } = useChildren(COLLAPSE_KEY);
 
-    const toggle = (name, expanded) => {
-      const { accordion, modelValue } = props;
-
-      if (accordion) {
-        if (name === modelValue) {
-          name = '';
-        }
-      } else if (expanded) {
-        name = modelValue.concat(name);
-      } else {
-        name = modelValue.filter((activeName) => activeName !== name);
-      }
-
+    const updateName = (name: number | string | Array<number | string>) => {
       emit('change', name);
       emit('update:modelValue', name);
     };
 
-    const isExpanded = (name) => {
+    const toggle = (name: number | string, expanded: boolean) => {
+      const { accordion, modelValue } = props;
+
+      if (accordion) {
+        updateName(name === modelValue ? '' : name);
+      } else if (expanded) {
+        updateName((modelValue as Array<number | string>).concat(name));
+      } else {
+        updateName(
+          (modelValue as Array<number | string>).filter(
+            (activeName) => activeName !== name
+          )
+        );
+      }
+    };
+
+    const isExpanded = (name: number | string) => {
       const { accordion, modelValue } = props;
 
       if (process.env.NODE_ENV !== 'production') {
@@ -56,7 +71,9 @@ export default createComponent({
         }
       }
 
-      return accordion ? modelValue === name : modelValue.indexOf(name) !== -1;
+      return accordion
+        ? modelValue === name
+        : (modelValue as Array<number | string>).indexOf(name) !== -1;
     };
 
     linkChildren({ toggle, isExpanded });