Abstract: In order to efficiently design good orthogonal phase coding signals for MIMO radar, an improved Gerchberg-Saxton(GS) algorithm is proposed. Firstly, a cost function minimizing the sidelobe energy of the signal set is constructed, and it is transformed into a easy-to-solve minimization problem. Then the original GS algorithm is extended to multi-dimensional form, and the object-domain and Fourier-domain constraints are improved accordingly for the optimization problem in this paper. Finally, the signal set is obtained by implementing the improved GS algorithm. Simulation results show that the proposed algorithm can improve the integrated sidelobes and the correlation property of the resulting waveform.