Provided is a smartkey system for reducing battery consumption. The smartkey system in a sleep mode wakes up at every certain interval, and first checks whether there is a fob near a vehicle. Only when there is the fob near the vehicle, the smartkey system receives authentication information from the fob to authenticate the fob. Therefore, an authentication operation is not performed when there is no fob near the vehicle, and thus, a wakeup time is shortened, thereby reducing an amount of dark current consumed by the vehicle. Moreover, the wakeup time of the smartkey system is shortened, thus securing a time margin that enables an additional operation to be performed in the sleep mode.