Disclosed is a method for synchronizing a radio port and a radio interface unit (RIU) in a WLL system, in which an asynchronous system is used for communication among radio ports, capable of providing timing synchronization between each radio port and each RIU associated therewith. The method involves the steps of controlling a modulator equipped in the radio port to execute an internal timing alignment thereof, controlling a channel card controller equipped in the radio port to execute the timing alignment with the modulator, controlling the channel card controller to transmit the synchronous data to the radio interface unit via the modulator, controlling the radio interface unit to acquire a pilot signal transmitted from the radio port, and synchronizing the radio interface unit with the radio port associated with the acquired pilot signal based on the synchronous data received from the radio port. In accordance with the method, the WLL system obtains synchronization between each radio port and RIU associated therewith, thereby maintaining stability. Therefore, it is unnecessary to use a separate unit such as GPS receivers and is possible to provide an inexpensive and reliable WLL system.