Abstract: Compared with conventional radar system, MIMO radar system has huge computation because of the large dimensions of echo data in receiving beamforming using MVDR or LCMV. Considering that the transmitted waveforms of MIMO radar is orthogonal to each other, the full-dimensional MIMO radar can be thought a combination of multiple SIMO radars in receiving beamforming after matched filter. This kind of equivalent not only reduces the dimensions and number of data snapshot, but also cuts down the computation when the covariance matrix and its inverse operation were calculated. In addition, the iterative solution is not required compared with the existing algorithm. Simulation results validates that the new method has a similar performance with the full-dimensional algorithm when the number of data snapshot is large enough, and keeps good performance as the number of data snapshot is fewer, meanwhile, the computation of the new method is greatly decreased compared to the full-dimensional method.