diff --git a/src/canvas/assets/canvas.css b/src/canvas/assets/canvas.css
deleted file mode 100644
index e42e6f7d..00000000
--- a/src/canvas/assets/canvas.css
+++ /dev/null
@@ -1 +0,0 @@
-.Canvas {}
\ No newline at end of file
diff --git a/src/demo/assets/demo.css b/src/demo/css/demo.css
similarity index 100%
rename from src/demo/assets/demo.css
rename to src/demo/css/demo.css
diff --git a/src/demo/index.tsx b/src/demo/index.tsx
index 03bea69b..aeb93afb 100644
--- a/src/demo/index.tsx
+++ b/src/demo/index.tsx
@@ -2,7 +2,7 @@ import React, { Component } from 'react';
 import Canvas from '../canvas';
 import mapping from '../mock/mapping.json';
 import Toolbar from '../tools';
-import './assets/demo.css';
+import './css/demo.css';
 
 export interface CanvasPosition {
   x: number;
diff --git a/src/line/core.tsx b/src/line/core.tsx
index 24eecd84..3d0d15a6 100644
--- a/src/line/core.tsx
+++ b/src/line/core.tsx
@@ -1,6 +1,6 @@
 import React, { PureComponent } from 'react';
 import classNames from 'classnames';
-import './assets/Line.css';
+import './css/Line.css';
 
 export interface LineProps {
   x0: number;
diff --git a/src/line/assets/Line.css b/src/line/css/Line.css
similarity index 100%
rename from src/line/assets/Line.css
rename to src/line/css/Line.css
diff --git a/src/tools/BlockGroup.tsx b/src/tools/BlockGroup.tsx
index 73792db7..4b61e708 100644
--- a/src/tools/BlockGroup.tsx
+++ b/src/tools/BlockGroup.tsx
@@ -3,7 +3,7 @@ import classNames from 'classnames';
 import Draggable from 'react-draggable';
 import { generateKey, stopPropagation } from '../utils/LineUtil';
 import omit from 'omit.js';
-import './assets/BlockGroup.css';
+import './css/BlockGroup.css';
 
 // one Line is mapping to two Block
 // to record it here
diff --git a/src/tools/TagGroup.tsx b/src/tools/TagGroup.tsx
index fb6c6045..6f0e1efb 100644
--- a/src/tools/TagGroup.tsx
+++ b/src/tools/TagGroup.tsx
@@ -2,7 +2,7 @@ import React, { Component } from 'react';
 import classNames from 'classnames';
 import Draggable from 'react-draggable';
 import { Input } from 'antd';
-import './assets/TagGroup.css';
+import './css/TagGroup.css';
 import { stopPropagation } from '../utils/LineUtil';
 
 export interface TagGroupProps {
diff --git a/src/tools/Toolbar.tsx b/src/tools/Toolbar.tsx
index 12466719..0b7ebce2 100644
--- a/src/tools/Toolbar.tsx
+++ b/src/tools/Toolbar.tsx
@@ -1,7 +1,7 @@
 import React, { Component } from 'react';
 import { Icon } from 'antd';
 import { tools } from '../options/tools';
-import './assets/Toolbar.css';
+import './css/Toolbar.css';
 
 export default class Toolbar extends Component {
   onDragStart = (e: any, item: any) => {
diff --git a/src/tools/assets/BlockGroup.css b/src/tools/css/BlockGroup.css
similarity index 100%
rename from src/tools/assets/BlockGroup.css
rename to src/tools/css/BlockGroup.css
diff --git a/src/tools/assets/TagGroup.css b/src/tools/css/TagGroup.css
similarity index 100%
rename from src/tools/assets/TagGroup.css
rename to src/tools/css/TagGroup.css
diff --git a/src/tools/assets/Toolbar.css b/src/tools/css/Toolbar.css
similarity index 100%
rename from src/tools/assets/Toolbar.css
rename to src/tools/css/Toolbar.css