diff --git a/doc/demo09_canvas/canvas.md b/doc/demo09_canvas/canvas.md
index 1e2855b..7352aa0 100644
--- a/doc/demo09_canvas/canvas.md
+++ b/doc/demo09_canvas/canvas.md
@@ -1,9 +1,28 @@
 # 1. CanvasItem之draw和update
 
-![Image text](image/canvas1.png)
-![Image text](image/canvas2.png)
-![Image text](image/canvas3.png)
-![Image text](image/canvas4.png)
-![Image text](image/canvas5.png)
-![Image text](image/canvas6.png)
-![Image text](image/canvas7.png)
+- Canvas是画布的意思，所以CanvasItem代表了就是可以被绘制节点，可以设置可视化界面和材质的颜色
+  ![Image text](image/canvas1.png)
+
+
+- 所有的2D节点和GUI节点都继承于CanvasItem节点
+  ![Image text](image/canvas2.png)
+
+
+- CanvasItem是按树的树的广度优先遍历顺序绘制的
+  ![Image text](image/canvas3.png)
+
+
+- draw指定了要绘制的东西
+  ![Image text](image/canvas4.png)
+
+
+- 当要draw绘制的改变了，需要调用update
+  ![Image text](image/canvas5.png)
+
+
+- hide和show，隐藏和现实节点
+  ![Image text](image/canvas6.png)
+
+
+- CanvasItem可以绘制直线，正方形，长方形，圆，图片
+  ![Image text](image/canvas7.png)