Provided is a power saving method for a mobile terminal, of a WiBro communication system, particularly for a standby mode. A power saving method for a mobile terminal having a modem for communicating with a base station and a host for controlling the modem, includes starting, at the mobile terminal, a timer if a resource withdrawal is determined through a negotiation with the base station; turning off power to the modem; determining whether the timer has expired; and turning on the power to the modem.