Welcome to Android P Beta
The Preview version of Android P will provide you all the features needed to improve the compatibility and development of your application for the next version of the Android. At present, Mi MIX 2S has joined the Android P Developer Preview program, which is free for developers to use. Simply download the preview tool and you will be able to use it immediately.

欢迎参与Android P 预览版计划
Android P 预览版将为您提供下一个版本的Android应用程序的兼容性和开发所需的所有功能。您的小米MIX 2S 现已加入Android P 预览版计划, 可以免费下载安装. 下载预览版安装之后您立即就可以使用了。

To download or opt-in to the developer-preview:

• Please don’t forget to backup your data before upgrading to Android P
• Please download the P developer preview build for Mix 2s here.
• Please opt-in to the P build via the fastboot method.
  

下载以及使用预览版:

• 升级至Android P 之前请务必备份好您的相关数据
• Android P 开发者预览版：点击下载
• 请通过线刷的方式进行升级
  

Points to note:
Please note that the Developer preview is not the final version, and some features may be missing or may not work.
Here is the list of known issues you may encounter with the Developer preview build.

• Play music keeps stopping when clicking Music library
• No response when editing video in Photos
• UI issues for landscape mode
• Phone keeps hanging when choosing Voicemail
• The voice search function crashes in Setting
• Unable to edit local video
• No internet showed in the notification bar
  

几点声明:
请牢记开发者预览版不是最终版本, 少数功能可能缺失或者无法使用
下面几项则是您可能会遇到的已知问题：

• 在Play music 点击音乐列表时会停止运行
• 相册应用中进行视频编辑时相册无响应
• 横屏模式下存在少许UI问题
• 选择语音信箱时电话挂起
• 语音搜索功能在设置中崩溃
• 无法编辑本地视频内容
• 状态栏中不显示网络
  

If you would like to opt-out or revert to the factory image, you can do so through the fastboot method here.
If you have any feedback, do let us know here.
To learn more about Android P preview, go to Google Developers page.

如果你想回退到之前的系统，可以通过刷回官方系统的形式回退
如果你有遇到任何问题，可以在这里进行反馈
更多Android P 预览版相关内容，您可以前往 Google Developers page.

原文出处：点击跳转