diff --git a/snake.py b/snake.py
index 3cd13f6..0995c3e 100644
--- a/snake.py
+++ b/snake.py
@@ -43,12 +43,14 @@ while True:
     else:
         y += 30
     position.append((x, y))
-    position.pop(0)
+    
     if x==apple_x and y==apple_y:
         num1=random.randint(1,21)
         num2=random.randint(1,16)
         apple_x=num1*30-30
         apple_y=num2*30-30
+    else:
+        position.pop(0)
     screen.blit(background, (0, 0))
     # 将贪吃蛇的头画上去
     screen.blit(snake_head, position[-1])