Abstract: Aiming at the low altitude target detection performance decline caused by the compound effect of low altitude multipath effect and ground clutter, the spatial and frequency diversity characters of the orthogonal frequency division multiplexing (OFDM) multiple-input multiple-output (MIMO) radar are used to improve the detection performance. Based on the establishment of the orthogonal frequency division multiplexing linear frequency modulation (OFDM-LFM) transmitting signal model, the multipath effect model and the ground clutter model based on symmetric alpha stable distribution, the spatial and frequency diversity character of OFDM-MIMO radar are analyzed and the compound received signal model is established. The matched filter is used to recover the signal from each transmitting-receiving pair. The signals are combined to realize the compensation irregularly, so as to avoid the deep energy depression and the severe fluctuation of the received signal. The simulation results show that the OFDM-MIMO radar can effectively reduce the effect on target detection caused by the severe fluctuation and the clutter of the received signals, and as a result, the stable detection is realized under multipath and clutter background.