How to cancel synchronization between Apple mobile phone and Apple computer?

Use a different Apple ID or turn off iCloud.

Here is an example of turning off iCloud function on iPhone 7. The specific method is as follows:

First, click "Settings" on the phone desktop.

2. After entering the phone setting interface, drop down the menu, and then select the "password and account number" option, as shown in the figure.

Third, then open "iCloud" to enter.

4. Click "iCloud Cloud Backup" to enter.

5. Finally, turn off the switch of "iCloud Cloud Backup".