diff --git a/lib/timewheel/timewheel.go b/lib/timewheel/timewheel.go
index a5263bd..ba3fe89 100644
--- a/lib/timewheel/timewheel.go
+++ b/lib/timewheel/timewheel.go
@@ -6,13 +6,18 @@ import (
 	"time"
 )
 
+type location struct {
+	slot  int
+	etask *list.Element
+}
+
 // TimeWheel can execute job after waiting given duration
 type TimeWheel struct {
 	interval time.Duration
 	ticker   *time.Ticker
 	slots    []*list.List
 
-	timer             map[string]int
+	timer             map[string]*location
 	currentPos        int
 	slotNum           int
 	addTaskChannel    chan task
@@ -35,7 +40,7 @@ func New(interval time.Duration, slotNum int) *TimeWheel {
 	tw := &TimeWheel{
 		interval:          interval,
 		slots:             make([]*list.List, slotNum),
-		timer:             make(map[string]int),
+		timer:             make(map[string]*location),
 		currentPos:        0,
 		slotNum:           slotNum,
 		addTaskChannel:    make(chan task),
@@ -99,12 +104,12 @@ func (tw *TimeWheel) start() {
 
 func (tw *TimeWheel) tickHandler() {
 	l := tw.slots[tw.currentPos]
-	tw.scanAndRunTask(l)
 	if tw.currentPos == tw.slotNum-1 {
 		tw.currentPos = 0
 	} else {
 		tw.currentPos++
 	}
+	go tw.scanAndRunTask(l)
 }
 
 func (tw *TimeWheel) scanAndRunTask(l *list.List) {
@@ -138,11 +143,18 @@ func (tw *TimeWheel) addTask(task *task) {
 	pos, circle := tw.getPositionAndCircle(task.delay)
 	task.circle = circle
 
-	tw.slots[pos].PushBack(task)
-
-	if task.key != "" {
-		tw.timer[task.key] = pos
+	e := tw.slots[pos].PushBack(task)
+	loc := &location{
+		slot:  pos,
+		etask: e,
 	}
+	if task.key != "" {
+		_, ok := tw.timer[task.key]
+		if ok {
+			tw.removeTask(task.key)
+		}
+	}
+	tw.timer[task.key] = loc
 }
 
 func (tw *TimeWheel) getPositionAndCircle(d time.Duration) (pos int, circle int) {
@@ -155,18 +167,11 @@ func (tw *TimeWheel) getPositionAndCircle(d time.Duration) (pos int, circle int)
 }
 
 func (tw *TimeWheel) removeTask(key string) {
-	position, ok := tw.timer[key]
+	pos, ok := tw.timer[key]
 	if !ok {
 		return
 	}
-	l := tw.slots[position]
-	for e := l.Front(); e != nil; {
-		task := e.Value.(*task)
-		if task.key == key {
-			delete(tw.timer, task.key)
-			l.Remove(e)
-		}
-
-		e = e.Next()
-	}
+	l := tw.slots[pos.slot]
+	l.Remove(pos.etask)
+	delete(tw.timer, key)
 }