In view of the defect of high complexity and the need for special pilot frame in the traditional MIMO-OFDM channel estimation algorithms, two improved channel estimation algorithms based on subcarrier grouping were researched. In improved algorithms, for avoiding the computation of large-scale matrix inverse operation and reducing algorithm complexity, channel responses of pilot subcarrier were obtained by single antenna channel estimation that is transformed from multi-antennas channel estimation by the method of subcarrier grouping. Then, channel responses of the whole frame signs were estimated with DFT filtering or LMS(Least Mean Square) adaptive filtering for better performance with complexity scarcely increasing. Theoretical analysis and simulation shows that the improved algorithms have lower complexity and better performance than the traditional channel estimation algorithms.