diff --git a/pkg/scheduler/actions/backfill/backfill.go b/pkg/scheduler/actions/backfill/backfill.go
new file mode 100644
index 000000000..95586e7f9
--- /dev/null
+++ b/pkg/scheduler/actions/backfill/backfill.go
@@ -0,0 +1,73 @@
+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package backfill
+
+import (
+	"github.com/golang/glog"
+
+	"github.com/kubernetes-sigs/kube-batch/pkg/scheduler/api"
+	"github.com/kubernetes-sigs/kube-batch/pkg/scheduler/framework"
+)
+
+type backfillAction struct {
+	ssn *framework.Session
+}
+
+func New() *backfillAction {
+	return &backfillAction{}
+}
+
+func (alloc *backfillAction) Name() string {
+	return "preempt"
+}
+
+func (alloc *backfillAction) Initialize() {}
+
+func (alloc *backfillAction) Execute(ssn *framework.Session) {
+	glog.V(3).Infof("Enter Backfill ...")
+	defer glog.V(3).Infof("Leaving Backfill ...")
+
+	// TODO (k82cn): When backfill, it's also need to balance between Queues.
+	for _, job := range ssn.Jobs {
+		for _, task := range job.TaskStatusIndex[api.Pending] {
+			if task.Resreq.IsEmpty() {
+				// As task did not request resources, so it only need to meet predicates.
+				// TODO (k82cn): need to prioritize nodes to avoid pod hole.
+				for _, node := range ssn.Nodes {
+					// TODO (k82cn): predicates did not consider pod number for now, there'll
+					// be ping-pong case here.
+					if err := ssn.PredicateFn(task, node); err != nil {
+						glog.V(3).Infof("Predicates failed for task <%s/%s> on node <%s>: %v",
+							task.Namespace, task.Name, node.Name, err)
+						continue
+					}
+
+					glog.V(3).Infof("Binding Task <%v/%v> to node <%v>", task.Namespace, task.Name, node.Name)
+					if err := ssn.Allocate(task, node.Name); err != nil {
+						glog.Errorf("Failed to bind Task %v on %v in Session %v", task.UID, node.Name, ssn.UID)
+						continue
+					}
+					break
+				}
+			} else {
+				// TODO (k82cn): backfill for other case.
+			}
+		}
+	}
+}
+
+func (alloc *backfillAction) UnInitialize() {}
diff --git a/pkg/scheduler/factory.go b/pkg/scheduler/factory.go
index 6290b1127..4f039736b 100644
--- a/pkg/scheduler/factory.go
+++ b/pkg/scheduler/factory.go
@@ -18,6 +18,7 @@ package scheduler
 
 import (
 	"github.com/kubernetes-sigs/kube-batch/pkg/scheduler/actions/allocate"
+	"github.com/kubernetes-sigs/kube-batch/pkg/scheduler/actions/backfill"
 	"github.com/kubernetes-sigs/kube-batch/pkg/scheduler/actions/preempt"
 	"github.com/kubernetes-sigs/kube-batch/pkg/scheduler/actions/reclaim"
 
@@ -43,5 +44,6 @@ func init() {
 	// Actions
 	framework.RegisterAction(reclaim.New())
 	framework.RegisterAction(allocate.New())
+	framework.RegisterAction(backfill.New())
 	framework.RegisterAction(preempt.New())
 }
diff --git a/pkg/scheduler/plugins/priority/priority.go b/pkg/scheduler/plugins/priority/priority.go
index 44687cd5c..bd134ee23 100644
--- a/pkg/scheduler/plugins/priority/priority.go
+++ b/pkg/scheduler/plugins/priority/priority.go
@@ -20,8 +20,6 @@ import (
 	"github.com/golang/glog"
 	"github.com/kubernetes-sigs/kube-batch/pkg/scheduler/api"
 	"github.com/kubernetes-sigs/kube-batch/pkg/scheduler/framework"
-
-	"k8s.io/api/core/v1"
 )
 
 type priorityPlugin struct {
@@ -39,11 +37,6 @@ func (pp *priorityPlugin) OnSessionOpen(ssn *framework.Session) {
 		lv := l.(*api.TaskInfo)
 		rv := r.(*api.TaskInfo)
 
-		// TODO quick fix, enhance it later by other option.
-		if res := compareQoS(lv.Pod, rv.Pod); res != 0 {
-			return res
-		}
-
 		glog.V(3).Infof("Priority TaskOrder: <%v/%v> prority is %v, <%v/%v> priority is %v",
 			lv.Namespace, lv.Name, lv.Priority, rv.Namespace, rv.Name, rv.Priority)
 
@@ -88,28 +81,3 @@ func (pp *priorityPlugin) OnSessionOpen(ssn *framework.Session) {
 }
 
 func (pp *priorityPlugin) OnSessionClose(ssn *framework.Session) {}
-
-// make BestEffort > Burstable/Guarantee
-func compareQoS(l, r *v1.Pod) int {
-	lq := l.Status.QOSClass
-	rq := r.Status.QOSClass
-
-	glog.V(3).Infof("Priority TaskOrder: <%v/%v> QoS is %v, <%v/%v> QoS is %v",
-		l.Namespace, l.Name, lq, r.Namespace, r.Name, rq)
-
-	if lq == rq {
-		return 0
-	}
-
-	// BestEffort > Burstable/Guarantee
-	if lq == v1.PodQOSBestEffort {
-		return -1
-	}
-
-	// Burstable/Guarantee < BestEffort
-	if rq == v1.PodQOSBestEffort {
-		return 1
-	}
-
-	return 0
-}
diff --git a/pkg/scheduler/util.go b/pkg/scheduler/util.go
index 92c14e8a2..72039387d 100644
--- a/pkg/scheduler/util.go
+++ b/pkg/scheduler/util.go
@@ -27,7 +27,7 @@ import (
 )
 
 var defaultSchedulerConf = map[string]string{
-	"actions":                   "reclaim, allocate, preempt",
+	"actions":                   "reclaim, allocate, backfill, preempt",
 	"plugins":                   "gang, priority, drf, predicates, proportion",
 	"plugin.gang.jobready":      "true",
 	"plugin.gang.joborder":      "true",