Abstract: To realize the high precision direction of arrival (DOA) of multiple input and multiple output (MIMO) radar, an effective solution was suggested in this paper by combining covariance method and matrix preprocessing algorithm. First, the MIMO radar signal model was modeled and simulated, and the covariance matrix was used to get the signal covariance matrix that was closer to the theoretical value, and the convex optimization method was introduced to solve the problem. In view of the influence of noise and coherent signals, the matrix preprocessing method was introduced to the received signal to be processed with extra processing, and then the unitary ESPRIT algorithm was used to jointly estimate the pitch angle and azimuth angle of the MIMO radar, so as to reduce the DOA estimation of the whole algorithm. Finally, the experiment results show that the proposed algorithm can effectively improve the DOA estimation accuracy of MIMO radar without increasing amount of computation.