diff --git a/README.md b/README.md
index bf7ec09..866064e 100644
--- a/README.md
+++ b/README.md
@@ -76,7 +76,7 @@ $ npm install postcss-px-to-viewport --save-dev
 ```
 or yarn
 ```
-$ yarn add postcss-px-to-viewport
+$ yarn add -D postcss-px-to-viewport
 ```
 
 ### Usage
diff --git a/README_CN.md b/README_CN.md
index 8ceb728..5b29e55 100644
--- a/README_CN.md
+++ b/README_CN.md
@@ -76,7 +76,7 @@ $ npm install postcss-px-to-viewport --save-dev
 ```
 或者使用yarn进行安装
 ```
-$ yarn add postcss-px-to-viewport
+$ yarn add -D postcss-px-to-viewport
 ```
 
 ### 配置参数