— It was shown by Cadambe and Jafar that the interference alignment (IA) algorithm achieves the theoretical bound on degrees of freedom (DOF) for interference channel systems. However, since this method addresses the precoder design problem from the DOF point of view, some optimization processes are additionally needed in order to improve the sum rate performance. In this paper, based on the IA method, we propose a two-stage optimization of the precoding and decoding matrices in the interference channels. Simulation results show that the proposed method significantly improves the sum rate of the conventional IA scheme while maintaining the optimality of the DOF.