How to back up iPhone 5s if it cannot be turned on?

1. It is recommended to press and hold the power button for 10 seconds, shut down and then restart.

2. Whether you can enter Recovery. How to enter Recovery: In the power-off state, first press and hold the "Volume Up Key" and then the "Power Off Key". Release when the startup screen appears to enter Recovery. If you can enter Recovery, please switch the system under Recovery and back up the data. If it fails, you need to clear all data (address book, text messages, mobile phone applications, etc. will disappear).

3. If the problem persists, it is recommended to re-flash the firmware.