Cooperative diversity transmission can get some diversity gain through the collaboration of other users, whereas the frequency selective fading channel performance is not optimistic. To counteract frequency selective fading, Orthogonal Frequency Division Multiplexing(OFDM) technology and cooperative diversity combining method are adopted to study collaborative communication based on OFDM technology. The system performance in different modulation techniques and different channel estimation methods is compared. The traditional S&C(Schmidl and Cox) algorithm is improved and applied to the system in order to further improve its performance. Simulation results show that the performance of improved timing synchronization is superior to that of the traditional S&C algorithm.