Abstract: OFDM is viewed as key technology of the next generation of wireless communication because of its strong ability of anti-multi-path and high frequency utility rate. The need for wireless data and multimedia services promotes the development and applications of many high-speed wireless communication techniques. Multiple Input and Multiple Output(MIMO) techniques and OFDM techniques have been or will be used in various high speed wireless systems. Doing research on the key technologies is very important. MIMO-OFDM has a same common with SISO-OFDM, it is very sensitive to timing synchronization error and carrier frequency offset, i.e., the frame structure or decoding could be damaged if timing or carrier frequency is out of synchronization. Correct symbol timing and precise carrier frequency offset estimation are necessary for MIMO-OFDM. This paper first applies CAZAC sequence to construct a conjugate staggered structure as training sequences, and then proposes an algorithm based on this structure to improve carrier frequency and timing synchronization by applying threshold method. Meanwhile, setups of the parameters that influence the threshold are determined according to the simulation results. The simulation results show that in multipath channel, the proposed method can reduce the BER of the system compared to the conventional method and effectively improve synchronization performance.