diff --git a/source/constants.py b/source/constants.py
index ae4ff13..41b6d0a 100755
--- a/source/constants.py
+++ b/source/constants.py
@@ -123,10 +123,8 @@ BACKGROUND_DAY_LIKE_BACKGROUNDS = { BACKGROUND_DAY, BACKGROUND_SINGLE,
 
 # 夜晚地图的墓碑数量等级
 GRADE_GRAVES = 'grade_graves'
-GRADE0_GRAVES = 0   # 无墓碑
-GRADE1_GRAVES = 1   # 少量墓碑
-GRADE2_GRAVES = 2   # 中等数量墓碑
-GRADE3_GRAVES = 3   # 大量墓碑
+# 不同墓碑等级对应的信息
+GRAVES_GRADE_INFO = (0, 4, 7, 11)
 
 # 僵尸生成方式
 SPAWN_ZOMBIES = 'spawn_zombies'
diff --git a/source/state/level.py b/source/state/level.py
index 6d4682a..1adcf96 100644
--- a/source/state/level.py
+++ b/source/state/level.py
@@ -473,20 +473,15 @@ class Level(tool.State):
         self.showHugeWaveApprochingTime = -2000 # 防止设置为0时刚刚打开游戏就已经启动红字
 
         if self.map_data[c.BACKGROUND_TYPE] == c.BACKGROUND_NIGHT:
+            # 判断墓碑数量等级
+            # 0为无墓碑，1为少量墓碑，2为中等量墓碑，3为大量墓碑
             if c.GRADE_GRAVES in self.map_data:
                 gradeGraves = self.map_data[c.GRADE_GRAVES]
             # 缺省为少量墓碑
             else:
-                gradeGraves = c.GRADE1_GRAVES
+                gradeGraves = 1
             
-            if gradeGraves == c.GRADE1_GRAVES:
-                graveVolume = 4
-            elif gradeGraves == c.GRADE2_GRAVES:
-                graveVolume = 7
-            elif gradeGraves >= c.GRADE3_GRAVES:
-                graveVolume = 11
-            else:
-                graveVolume = 0
+            graveVolume = c.GRAVES_GRADE_INFO[gradeGraves]
             self.graveSet = set()
             while len(self.graveSet) < graveVolume:
                 mapX = randint(4, 8)    # 注意是从0开始编号