This paper analysis the principle and properties of the direct power control (DPC) system for present three phase PWM rectifiers based on its mathematical model. Switching table in power loop of DPC system controls instantaneous active power and reactive power, Switching table is related to system performance, in order to meet the different requirements, a detailed analysis of the switch table design methods to be study, an improvement switching table is designed to overcome the shortcomings of conventional switching table, it achieved good result for power control. Simulation results verify the new switching table design method.