diff --git a/plan/physical_plan_builder.go b/plan/physical_plan_builder.go
index d96e451ea6..fa383ff4fb 100644
--- a/plan/physical_plan_builder.go
+++ b/plan/physical_plan_builder.go
@@ -31,7 +31,7 @@ const (
 	selectionFactor = 0.8
 	distinctFactor  = 0.7
 	cpuFactor       = 0.9
-	aggFactor       = 0.2
+	aggFactor       = 0.1
 	joinFactor      = 0.3
 )
 
@@ -359,7 +359,7 @@ func enforceProperty(prop *requiredProperty, info *physicalPlanInfo) *physicalPl
 		if prop.limit != nil {
 			count = prop.limit.Offset + prop.limit.Count
 		}
-		info.cost += float64(info.count)*cpuFactor + float64(count)*memoryFactor
+		info.cost += sortCost(count)
 	} else if prop.limit != nil {
 		limit := prop.limit.Copy()
 		limit.SetSchema(info.p.GetSchema())
@@ -371,6 +371,10 @@ func enforceProperty(prop *requiredProperty, info *physicalPlanInfo) *physicalPl
 	return info
 }
 
+func sortCost(cnt uint64) float64 {
+	return float64(cnt)*math.Log2(float64(cnt))*cpuFactor + memoryFactor*float64(cnt)
+}
+
 // removeLimit removes the limit from prop.
 func removeLimit(prop *requiredProperty) *requiredProperty {
 	ret := &requiredProperty{
@@ -948,8 +952,7 @@ func (p *Sort) convert2PhysicalPlan(prop *requiredProperty) (*physicalPlanInfo,
 	if err != nil {
 		return nil, errors.Trace(err)
 	}
-	cnt := float64(unSortedPlanInfo.count)
-	sortCost := cnt*math.Log2(cnt)*cpuFactor + memoryFactor*cnt
+	sortCost := sortCost(unSortedPlanInfo.count)
 	if len(selfProp.props) == 0 {
 		np := p.Copy().(*Sort)
 		np.ExecLimit = prop.limit
diff --git a/plan/plan_test.go b/plan/plan_test.go
index 288b011ea8..7062e7c11c 100644
--- a/plan/plan_test.go
+++ b/plan/plan_test.go
@@ -922,6 +922,10 @@ func (s *testPlanSuite) TestCBO(c *C) {
 			sql:  "select count(*) from t t1 having 1 = 0",
 			best: "Dummy->HashAgg->Selection",
 		},
+		{
+			sql:  "select sum(a.b), sum(b.b) from t a join t b on a.c = b.c group by a.d order by a.d",
+			best: "LeftHashJoin{Table(t)->Table(t)}(a.c,b.c)->HashAgg->Sort->Trim",
+		},
 		{
 			sql:  "select count(*) from t group by c",
 			best: "Index(t.c_d_e)[[<nil>,+inf]]->StreamAgg",