diff --git a/.eslintignore b/.eslintignore
index dadc716f..2e7d2a0c 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -1,3 +1,3 @@
 **/dist
-**/es
+**/esm
 **/cjs
diff --git a/.prettierignore b/.prettierignore
index b35bbe9c..4b638db9 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -3,5 +3,5 @@ package-lock.json
 lerna.json
 CHANGELOG.md
 **/dist
-**/es
+**/esm
 **/cjs
diff --git a/package.json b/package.json
index 450b3c6a..9f5db072 100644
--- a/package.json
+++ b/package.json
@@ -40,7 +40,7 @@
     "build": "yarn build:lib && yarn build:standalone",
     "build:watch": "lerna run build:watch --stream --parallel",
     "release": "yarn build && lerna publish",
-    "start": "yarn workspace example run start"
+    "start": "npm run build:watch & yarn workspace example run start"
   },
   "devDependencies": {
     "@babel/cli": "^7.1.5",
diff --git a/packages/griffith-mp4/src/mse/controller.js b/packages/griffith-mp4/src/mse/controller.js
index ce1ac4e3..73a7b55a 100644
--- a/packages/griffith-mp4/src/mse/controller.js
+++ b/packages/griffith-mp4/src/mse/controller.js
@@ -83,11 +83,33 @@ export default class MSE {
       })
   }
 
+  hasBufferedCache = (time = 0) => {
+    const buffered = this.video.buffered
+
+    if (buffered) {
+      for (let i = 0; i < buffered.length; i++) {
+        if (time >= buffered.start(i) && time <= buffered.end(i)) {
+          return true
+        }
+      }
+    }
+
+    return false
+  }
+
   seek = time => {
     FragmentFetch.clear()
 
     const [start, end] = this.mp4Probe.getFragmentPosition(time)
     this.mseUpdating = true
+
+    // 对于已经请求的数据不再重复请求
+    // No need to repeat request video data
+    const timeRange = this.mp4Probe.timeRange || []
+    if (this.hasBufferedCache(timeRange[1])) {
+      return
+    }
+
     this.loadData(start, end).then(mdatBuffer => {
       if (!mdatBuffer) {
         return