diff --git a/bullet.py b/bullet.py
index 0da35b8..d5503a5 100644
--- a/bullet.py
+++ b/bullet.py
@@ -58,4 +58,11 @@ class BossBullet(Sprite):
 
         self.color = ai_settings.bossbullet_color
         self.speed_factor = ai_settings.bossbullet_speed_factor
-        self.height = ai_settings.bossbullet_height
\ No newline at end of file
+        self.height = ai_settings.bossbullet_height
+
+    def update(self):
+        """向下移动子弹"""
+        # 更新表示子弹位置的小数值
+        self.y += self.speed_factor
+        # 更新表示子弹的rect的位置
+        self.rect.y = self.y