My kid found a Apple Watch. I tried to find owner but it has password lock is there other ways to find owner

You could press and hold the round button (if it is the cellular button) to initiate Siri and say "Call me". That may pull up the owner. I am not sure if it will work while locked, but it is worth a try.

Unless the owner left a message on the watch there is nothing you can do,hand it in to the police it might be reported as lost.