A locking system and a manufacturing method thereof, a bearing assembly, and a robot having the same. The locking system incudes a first nut arranged on a shaft and adapted to contact with an upper side of an inner ring of the bearing. The locking system can also include a second nut arranged on the shaft and separated from the first nut at a predetermined distance. The locking system can include a locking screw adapted to be screwed through a first through hole of the second nut and a second through hole of the first nut while the first through hole and the second through hole are aligned with each other.