A method for controlling sleep mode of a base station and a mobile station in wireless communication networks, including: determining N of the N-ary exponential sleep mode to decide a length of sleep duration including a sleep interval; measuring downlink traffic addressed to the mobile station at the beginning of a listening interval right after the sleep interval; and when there exist downlink traffic, confirming whether the measured downlink traffic satisfies a mode transition condition. The method further includes: conducting a sleep interval of the next sleep duration of which the length is determined by multiplying the length of the current sleep duration by N unless the downlink traffic satisfies the mode transition condition; and transmitting the downlink traffic to the mobile station when m times the additional consecutive sleep duration is expired or when the measured amount of the downlink traffic satisfies the mode transition condition.