diff --git a/snake.py b/snake.py
index 8484262..7d37b0c 100644
--- a/snake.py
+++ b/snake.py
@@ -65,6 +65,8 @@ while True:
         apple_y = num2* 30 - 30
     else:
         position.pop(0)
+    if x < 0 or x > 630 or y < 0 or y > 450:
+        exit()
     # 将背景图画上去
     screen.blit(background, (0, 0))
     # 将贪吃蛇的头画上去