Abstract: There is a dense relationship between the frequency offset estimation and channel estimation in Orthogonal Frequency Division Multiplexing (OFDM) systems. A new combined symbol timing and frequency synchronization and channel estimation technique by using the detected data is developed for OFDM systems. The synchronization information contained in the channel estimated results which is gained by LS channel estimation method is extracted based on the Maximum Likelihood (ML) criterion for synchronization estimation. Then the estimated results of symbol timing and frequency are used to correct the initial estimated channel and make it more close to the real channel. Simulation results show that this algorithm has better performance at high SNR. It is easy to be realized and has low complexity. Increasing the length of the data block suppresses the noise more effectively but decreases the ability of tracking the time variable channel. The block size should be a trade-off between them.