diff --git a/packages/dropdown-menu/README.md b/packages/dropdown-menu/README.md
index 967110af..ce975191 100644
--- a/packages/dropdown-menu/README.md
+++ b/packages/dropdown-menu/README.md
@@ -185,3 +185,9 @@ Page({
 | text  | 文字                             | _string_           |
 | value | 标识符                           | _number \| string_ |
 | icon  | 左侧[图标名称](#/icon)或图片链接 | _string_           |
+
+### 外部样式类
+
+| 类名         | 说明         |
+| ------------ | ------------ |
+| custom-class | 根节点样式类 |
diff --git a/packages/dropdown-menu/index.wxml b/packages/dropdown-menu/index.wxml
index 037ac3b6..cfd661d1 100644
--- a/packages/dropdown-menu/index.wxml
+++ b/packages/dropdown-menu/index.wxml
@@ -1,7 +1,7 @@
 <wxs src="../wxs/utils.wxs" module="utils" />
 <wxs src="./index.wxs" module="computed" />
 
-<view class="van-dropdown-menu van-dropdown-menu--top-bottom">
+<view class="van-dropdown-menu van-dropdown-menu--top-bottom custom-class">
   <view
     wx:for="{{ itemListData }}"
     wx:key="index"