diff --git a/README.md b/README.md
index cc73c3a85..72dbd818f 100644
--- a/README.md
+++ b/README.md
@@ -96,6 +96,7 @@ The following APIs are shared by Slider and Range.
 
 | Name         | Type    | Default | Description |
 | ------------ | ------- | ------- | ----------- |
+| prefixCls | string | `rc-tooltip` | Prefix class name |
 | className | string | `''` | Additional CSS class for the root DOM node |
 | min | number | `0` | The minimum value of the slider |
 | max | number | `100` | The maximum value of the slider |