Abstract: For the multiple-input multiple output(MIMO) system without beamforming, this paper proposes an algorithm using the spacial correlation of the interference signal to cancel the co-channel interference, and presents the ML algorithm for estimating this correlation. The simulation results demonstrates that this algorithm has a 3dB gain at BER=10-2 than the method of treating the interference as Gaussian noise in 2×2 Alamouti scheme, and 2×4 has a distinct advantage in 2×4 multiplexing scheme with a strong interference.