Abstract: Generally in MIMO system, the tradeoff between multiplexing gain and diversity gain，under their definite product, can be obtained by decreasing the efficiency of space-time code. In this paper, according to analyzing the relationship among the VBLAST, HARQ and STBC, a novel HARQ scheme that implement the combining between space-time code and HARQ smoothly, was proposed. On the premise of full multiplexing gain, the HARQ delay can be transform into SNR gain, introducing diversity gain superfluity. Furthermore, the relationship among the channel correlation, retransmitting time and spatial diversity is deeply and systemically analyzed in the paper. The simulation results show the effectiveness of the proposed scheme.