How Windows Phone phones restore factory settings

If the phone can boot normally: in the application list, click Settings > About > Reset phone.

If the phone does not boot, follow these steps:
1. Press the Power key to start the phone.

2. Quickly press the volume down key until the exclamation point (!) interface appears on the screen. The interface prompts you that your phone is about to resume factory settings.

3. In turn, press the volume up key, the volume down key, the power button, the volume down key.

4. Your phone will be restarted and restored to the factory setting state.