diff --git a/server/gameserver/car.cc b/server/gameserver/car.cc
index 61dee03..aadf1e4 100644
--- a/server/gameserver/car.cc
+++ b/server/gameserver/car.cc
@@ -487,8 +487,8 @@ float Car::GetMaxOil()
 
 void Car::DropItems(Obstacle* obstacle)
 {
-    if (obstacle->meta->i->drop() != 0) {
-        room->ScatterDrop(obstacle->GetPos(), obstacle->meta->i->drop());
+    if (obstacle->meta->HasDrop()) {
+        room->ScatterDrop(obstacle->GetPos(), obstacle->meta->RandDrop());
     }
 }
 
diff --git a/server/gameserver/hero.cc b/server/gameserver/hero.cc
index 37e3af3..5311018 100644
--- a/server/gameserver/hero.cc
+++ b/server/gameserver/hero.cc
@@ -389,7 +389,7 @@ void Hero::DropItems(Obstacle* obstacle)
     if (obstacle->IsEntitySubType(EST_RoomObstacle)) {
         is_treasure_box = ((RoomObstacle*)obstacle)->is_treasure_box;
     }
-    int drop_id = obstacle->meta->i->drop();
+    int drop_id = obstacle->meta->RandDrop();
     if (drop_id == 0) {
         return;
     }
diff --git a/server/gameserver/human.cc b/server/gameserver/human.cc
index e4d3cd6..da42f6c 100644
--- a/server/gameserver/human.cc
+++ b/server/gameserver/human.cc
@@ -2271,7 +2271,7 @@ void Human::DropItems(Obstacle* obstacle)
     if (obstacle->IsEntitySubType(EST_RoomObstacle)) {
         is_treasure_box = ((RoomObstacle*)obstacle)->is_treasure_box;
     }
-    int drop_id = obstacle->meta->i->drop();
+    int drop_id = obstacle->meta->RandDrop();
     if (drop_id == 0) {
         return;
     }
@@ -2290,7 +2290,7 @@ void Human::DropItems(Obstacle* obstacle)
     }
 
     if (drop_id == 0) {
-        drop_id = obstacle->meta->i->drop();
+        drop_id = obstacle->meta->RandDrop();
     }
     room->ScatterDrop(obstacle->GetPos(), drop_id);
     if (is_treasure_box) {
diff --git a/server/gameserver/metadata.cc b/server/gameserver/metadata.cc
index 9ceed91..3830936 100644
--- a/server/gameserver/metadata.cc
+++ b/server/gameserver/metadata.cc
@@ -207,9 +207,36 @@ namespace MetaData
     {
         {
             std::vector<std::string> strings;
-            a8::Split(i->buff_list(), strings, '|');
-            for (const std::string& tmp_str : strings) {
-                buff_list.push_back(a8::XValue(tmp_str));
+            a8::Split(i->preexplosion_summon(), strings, '|');
+            for (const std::string& str : strings) {
+                std::vector<std::string> strings2;
+                a8::Split(str, strings2, ':');
+                assert(strings2.size() == 2);
+                preexplosion_summon.push_back
+                    (std::make_tuple(
+                                     a8::XValue(strings2[0]),
+                                     a8::XValue(strings2[1])
+                                     )
+                     );
+            }
+        }
+        {
+            int total_weight = 0;
+            std::vector<std::string> strings;
+            a8::Split(i->drop(), strings, '|');
+            for (const std::string& str : strings) {
+                std::vector<std::string> strings2;
+                a8::Split(str, strings2, ':');
+                assert(strings2.size() == 2);
+                int drop_id = a8::XValue(strings2[0]);
+                int weight = a8::XValue(strings2[1]);
+                total_weight += weight;
+                drop.push_back
+                    (std::make_tuple(
+                                     drop_id,
+                                     total_weight
+                                     )
+                     );
             }
         }
         {
@@ -269,6 +296,20 @@ namespace MetaData
         }
     }
 
+    int MapThing::RandDrop()
+    {
+        if (HasDrop()) {
+            int total_weight = std::get<1>(drop[drop.size() - 1]);
+            int rnd = rand() % total_weight;
+            for (auto& tuple : drop) {
+                if (rnd < std::get<1>(tuple)) {
+                    return std::get<0>(tuple);
+                }
+            }
+        }
+        return 0;
+    }
+
     void Equip::Init()
     {
         {
diff --git a/server/gameserver/metadata.h b/server/gameserver/metadata.h
index 86606b7..a48d8a5 100644
--- a/server/gameserver/metadata.h
+++ b/server/gameserver/metadata.h
@@ -59,8 +59,12 @@ namespace MetaData
 	float float_param2 = 0;
         long long sweep_tags = 0;
         std::vector<int> param2_list;
+        std::vector<std::tuple<int, int>> preexplosion_summon;
+        std::vector<std::tuple<int, int>> drop;
+        bool HasDrop() { return !drop.empty();};
 
         void Init();
+        int RandDrop();
     };
 
     struct SafeArea
diff --git a/server/gameserver/obstacle.cc b/server/gameserver/obstacle.cc
index 990c2a9..aa0430e 100644
--- a/server/gameserver/obstacle.cc
+++ b/server/gameserver/obstacle.cc
@@ -577,8 +577,8 @@ void Obstacle::OnExplosionHit(Explosion* e)
     }
     if (IsDead(e->GetRoom())) {
         ProcDieExplosion(e->GetRoom());
-        if (meta->i->drop() != 0) {
-            e->GetRoom()->ScatterDrop(GetPos(), meta->i->drop());
+        if (meta->HasDrop()) {
+            e->GetRoom()->ScatterDrop(GetPos(), meta->RandDrop());
         }
         if (meta->i->thing_type() == kObstacleOilBucket) {
             MetaData::MapThing* bomb_meta = MetaMgr::Instance()->GetMapThing(meta->int_param1);
@@ -707,7 +707,7 @@ int Obstacle::OnCollisionTrigger(Creature* c, ColliderComponent* collider)
     case kCollisionHitDeadAndDrop:
         {
             if (c->room->GetGasData().gas_mode != GasInactive &&
-                meta->i->drop() != 0 &&
+                meta->HasDrop() &&
                 c->IsHuman()) {
                 Die(c->room);
                 c->DropItems(this);
diff --git a/server/gameserver/roomobstacle.cc b/server/gameserver/roomobstacle.cc
index 1950227..978a672 100644
--- a/server/gameserver/roomobstacle.cc
+++ b/server/gameserver/roomobstacle.cc
@@ -338,6 +338,7 @@ void RoomObstacle::ActiveSelfExplosion()
          [] (const a8::XParams& param)
          {
              RoomObstacle* obstacle = (RoomObstacle*)param.sender.GetUserData();
+             obstacle->InstallPreExplostionSummonTimer();
              obstacle->room->xtimer.AddRepeatTimerAndAttach
                  (
                   obstacle->meta->i->explosion_interval() / FRAME_RATE_MS,
@@ -678,3 +679,27 @@ void RoomObstacle::PushCollisionObjects()
              }
          });
 }
+
+void RoomObstacle::InstallPreExplostionSummonTimer()
+{
+    if (!meta->preexplosion_summon.empty()) {
+        int base_time = 0;
+        for (auto& tuple : meta->preexplosion_summon) {
+            int time = std::get<0>(tuple);
+            int obstacle_id = std::get<1>(tuple);
+            room->xtimer.AddDeadLineTimerAndAttach
+                (
+                 (base_time + time) / FRAME_RATE_MS,
+                 a8::XParams()
+                 .SetSender(this)
+                 .SetParam1(obstacle_id),
+                 [] (const a8::XParams& param)
+                 {
+                     RoomObstacle* obstacle = (RoomObstacle*)param.sender.GetUserData();
+                 },
+                 &xtimer_attacher.timer_list_
+                 );
+        }
+        base_time += meta->i->explosion_interval();
+    }
+}
diff --git a/server/gameserver/roomobstacle.h b/server/gameserver/roomobstacle.h
index afd4b79..7be8491 100644
--- a/server/gameserver/roomobstacle.h
+++ b/server/gameserver/roomobstacle.h
@@ -56,6 +56,7 @@ private:
     void SummonAirDropBox(int box_id);
     void ProcKeepRangeBuff();
     void DetachFromMaster();
+    void InstallPreExplostionSummonTimer();
 
 protected:
     RoomObstacleWeakPtr weak_ptr_;
diff --git a/server/tools/protobuild/metatable.proto b/server/tools/protobuild/metatable.proto
index 53fa69f..9760a54 100755
--- a/server/tools/protobuild/metatable.proto
+++ b/server/tools/protobuild/metatable.proto
@@ -51,7 +51,7 @@ message MapThing
     optional int32 hp = 5; //生命
     optional float damage = 6; //伤害
     optional float damage_dia = 7; //伤害半径
-    optional int32 drop = 8; //掉落
+    optional string drop = 8; //掉落
     optional int32 is_door = 10; //是否门
     optional int32 is_house = 11; //是否房间
     optional int32 is_tree = 12; //是否树
@@ -61,6 +61,7 @@ message MapThing
     optional int32 explosion_interval = 18;
     optional int32 explosion_times = 19;
     optional int32 explosion_float = 20;
+    optional string preexplosion_summon = 35;
     optional string monster_list = 21;
     optional string special_damage_type = 22;
     optional string receive_special_damage_type = 23;