diff --git a/planner/core/task.go b/planner/core/task.go
index 5beab58cac92d..a3e8a72f01bbc 100644
--- a/planner/core/task.go
+++ b/planner/core/task.go
@@ -1759,9 +1759,7 @@ func (p *PhysicalHashAgg) attach2TaskForMpp(tasks ...task) task {
 
 			prop := &property.PhysicalProperty{TaskTp: property.MppTaskType, ExpectedCnt: math.MaxFloat64, MPPPartitionTp: property.HashType, MPPPartitionCols: partitionCols}
 			newMpp := mpp.enforceExchanger(prop)
-			newMpp.addCost(middleAgg.GetCost(newMpp.count(), false, true, 0))
 			attachPlan2Task(middleAgg, newMpp)
-			middleAgg.SetCost(newMpp.cost())
 			mpp = newMpp
 		}