Abstract: The optimal design method of grid-connected inverter controller parameters based on D-partition method is researched in this paper. Considering the discrete characteristic of digital control,this paper derives the establishment conditions employing D-partition method in Z-domain and compares them with the results derived by using D-partition method in S-domain. According to the performance requirements of the system. The z-domain D-partition method is used to obtain the regulator parameter space domain under the requirement of the expected phase margin and magnitude margin,and the robustness. On this basis,the inverter bandwidth is taken as the objective function to optimize the controller parameters in the parameter space domain. The visualization analysis method does not need repeated trial and error on parameters. Instead,its setting goals are visual and clear. Simulation and experiment prove the correctness and validity of this method.