For multiple-input multiple-output with orthogonal frequency division multiplexing（MIMO-OFDM） systems

the error floor（EF） phenomenon at high signal noise rate（SNR） was induced by the expectation maximum（EM） channel estimation algorithm.In addition

the data transmission efficiency was declined obviously with the increasing number of transmit antennas.According to these problems

an improved and efficient EM channel estimation algorithm was pro-posed.Firstly

an accurate and equivalent signal model was introduced to derive a modified EM algorithm

which im-proved the estimation performance at high SNR.Next

to enhance the data transmission efficiency and further the esti-mate performance of the proposed algorithm

phase orthogonal pilots sequences and joint estimation were carried out over multiple OFDM symbols respectively.Simulation results show that the proposed algorithm has better estimation performance and higher data transmission efficiency.