Smart key system for the reduction of the battery consumption and method thereof

Disclosed is a smartkey system capable of checking whether there is a fob around a vehicle first by waking up a vehicle smartkey which is in a sleep mode, receiving authentication information from the fob only when there is the fob around the vehicle, and performing a fob authentication, thereby reducing the wakeup time by omitting the authentication that is performed even when there is not the fob around the vehicle, and reducing dark current consumption of the vehicle. Furthermore, as the wakeup time of the vehicle smartkey system is reduced, a time margin can be secured to additionally realize another motion within a cycle of the sleep mode.