You are using version 6.4.1 of the AdMob SDK which is non-compliant with the Google Play Ad Policy

You are using version 6.4.1 of the AdMob SDK which is non-compliant with the Google Play Ad Policy (http://goo.gl/6OZelH). On August 1st, 2014, Google Play will stop accepting updates to apps using this SDK. Upgrade to Google Play services now to avoid
this deadline

八月起Google Play不允许使用独立admob sdk的app

8月1日后，使用原本独立sdk的app会继续收到广告，但Play Store不再接收使用独立sdk的app。官方推荐使用google play service中的admob sdk.

问题是中国大部分安卓没有play service（因为play服务要向手机厂商收费）

Deprecating the Standalone AdMob SDK on 1 August 2014

Now that Google Mobile Ads is supported in Google Play services, we'll be deprecating the standalone AdMob SDK on 1 August of this year. Play services supports Advertising ID, and provides seamless updates to Android users.

On 1 August, the Play Store will stop accepting new or updated apps that use the standalone Google AdMob SDK. The standalone SDK does not use the Advertising ID, and will therefore be affected by the Google Play Ad Policy. Google Play services still supports
devices that don't have the Google Play store installed on it. The only difference is that devices without the Play Store will not receive automatic updates.

We strongly encourage you to update your apps prior to this date. Please see our blog post for more info.

http://googleadsdeveloper.blogspot.hk/2014/02/since-joining-google-play-services-back.html