diff --git a/docs/chapter_tree/binary_tree.md b/docs/chapter_tree/binary_tree.md
index 18db2d51c..f83ebee37 100644
--- a/docs/chapter_tree/binary_tree.md
+++ b/docs/chapter_tree/binary_tree.md
@@ -651,7 +651,7 @@
### 完全二叉树
-如下图所示,完全二叉树(complete binary tree)只有最底层的节点未被填满,且最底层节点尽量靠左填充。
+如下图所示,完全二叉树(complete binary tree)只有最底层的节点未被填满,且最底层节点尽量靠左填充。请注意,完美二叉树也是一棵完全二叉树。
![完全二叉树](binary_tree.assets/complete_binary_tree.png)