A system for dynamically shifting beacons in a distributed wireless network and a method thereof are disclosed. In a medium access control for a wireless personal area network based on a mobile ad-hoc network, beacons are shifted to other free lower slots in order to reduce the size of a beacon period. Also, collisions that may occur during the shifting of the beacons are detected and avoided. According to the system and method, the size of the beacon period for transmitting data can sufficiently be secured by dynamically reducing the size of the beacon period without collisions.