diff --git a/backend/modules/shop/logic/ShopManager.php b/backend/modules/shop/logic/ShopManager.php
index 8a4a2bb..d81c36f 100644
--- a/backend/modules/shop/logic/ShopManager.php
+++ b/backend/modules/shop/logic/ShopManager.php
@@ -12,6 +12,7 @@ class ShopManager
     const UNIT_TYPE_WEIGHT = 1; //重量
     const UNIT_TYPE_MONEY = 2;  //金额
     const UNIT_TYPE_ITEM = 3;   //件
+    const UNIT_TYPE_LENGTH = 4; //长度，宽度，高度，直径
 
     /**
      * @param $type
@@ -30,6 +31,9 @@ class ShopManager
             case self::UNIT_TYPE_ITEM:
                 return 1;   //后台显示和数据库都为件
                 break;
+            case self::UNIT_TYPE_LENGTH:
+                return 1;   //后台和数据库都为毫米
+                break;
             default:
                 return 1;
         }