The present invention relates to a method and device for authorizing user equipment (UE) in a wireless communication system. The present invention also relates to a method and device for authorizing authorized true user equipment if an abnormal power down report is transmitted from a fake user equipment. The real user equipment checks the abnormal power down from a base station, receives an assignment A-MAP 1E, and transmits an authorized message to the base station if power is not abnormally down. Alternatively, user equipment transmits, to the base station, an abnormal power down signaling header that includes authorization parameters, such as COUNTER_TEK or a cipher-based message authentication code (CMAC).