The invention discloses a method for realizing time synchronization in a wireless communication system. The method comprises the following steps of: determining initial receiving time of an uplink frame through an access point according to initial time, a downlink transmission period and a guard interval length of a downlink frame; determining the initial time when the downlink frame reaches a subscriber station according to synchronous leading of the downlink frame; and determining an uplink transmission time according to the downlink transmission period and the guard interval length. The invention also provides a corresponding wireless communication system. By using the method, data transmitting and receiving time points are respectively and independently determined through access points and subscriber stations, so that the access point and the subscriber station can be communicated with each other in order, and the synchronization process is simplified.