Swipe down from the top of the screen to access the Quick Settings panel , then tap the gear icon (Settings). Alternatively, press the crown to open the app list and find the Settings app.
Scroll down and tap Disconnect & reset .
Scroll down and tap Unpair device or Factory reset (wording may vary by app version). How to Hard Reset XIAOMI Watch S1
Tap on the Device tab (usually located at the bottom of the screen).
Wake up the watch screen by pressing the crown (top button). Swipe down from the top of the screen
Scroll through the Settings menu and tap on System .
Open the Mi Fitness app on your paired smartphone. and within minutes
Remember to sync your data beforehand, and within minutes, your watch will be ready for a fresh start.