MIMO radar has obvious advantage of the target detection performance compared with the traditional radar by using space diversity and waveform diversity technology, and becomes a research hot spot of future radar. In this paper, author gives the MIMO radar detection model based on the condition of clutter and noise, and deduces the theoretical formula of the detection performance. Its detection performance is compared with phased array radar under the multiple pulse accumulation conditions. The simulation result shows that when the SNR more than 10 dB, MIMO radar has obvious advantages.