How to change the battery of the watch?

It depends on what kind of bottom cover is used at the bottom of your watch. If it's a round bottom cover, and there are six equally spaced pits on the bottom cover, then rotate it inward, and you can rotate it counterclockwise. If it is round, but there is no pit on it, you can see if there is a small gap on the side at 1 1, insert the blade into this gap and pry it hard to open it. If it is square, this method is also used without screws. Pry it up. As long as there are screws, just screw them out. Needless to say, just change the battery.