Abstract: The mutual coupling effects and gain-phase errors can drastically degrade the direction estimation performance of multiple input multiple output (MIMO) radar array. Based on the Capon beamforming algorithm, a new auto-calibration method is proposed. The Toeplitz structure is exploited to reduce the number of unknown parameters. Using the property of Kronecker product, the transmitting and receiving array uncertainties can be decoupled for the error compensation at each iteration. Finally, the estimation of the target direction can be obtained. Simulation results verify the validity of the proposed algorithm.