You Can Download Go Keyboard From Google Play Store.After that you can follow this step.
Setting>>Language and input>>choose your keyboard.

i. Use Google Pinyin Input.
You can use Google Pinyin Input (keyboard) to input Chinese and English.

1. Download Google Pinyin Input from the Google Play store.
2. Once downloaded, you can open the app and follow the on screen to select it as your default keyboard.

i. SwiftKey keyboard
If you’re currently using SwiftKey keyboard, you can follow the steps below to add Chinese input.

1. From your device’s Settings, tap Additional settings > Language & input.
2. Tap the button next to SwiftKey Keyboard.
3. Tap Languages.
4. Check the box next to Chinese.
5. On the SwiftKey keyboard, you can swipe on the Spacebar to switch between languages.

I just download “Go keyboard” finally I could write Chinese words instead of, English with my xiaomi 5. Thanks, 谢谢