Abstract: The underwater acoustic MIMO communication technique based on VBLAST code is proposed to obtain high data rate.The technique can realize spatial multiplexing with multiple transmitters and receivers simultaneously to greatly increase data rate without increasing the system bandwidth.Robust coherent demodulation technique based on space-time adaptive decision-feedback equalization is proposed.The technique can efficiently suppress multi-path in-terference,co-channel interference and rapid phase fluctuation of MIMO channel.In addition,it can track the variable channel adaptively.Good performance is demonstrated by both simulation and lake trial results.