Abstract: Principles of traditional ip-iq method using low-pass filter and improved ip-iq method using current average filter were analyzed, and simulation experiment were made. The simulation result showed that independently using the traditional ip-iq method to filter exists bigger ripper in output waveform of current, and independently using current average method to filter can improve dynamic response speed, but its detection result is easy to be influenced by change of fundamental current. In order to solve the problems, an optimized ip-iq method which combining low-pass filter and current average filter was proposed, and simulation experiment was made. The simulation result showed that the optimized ip-iq method not only has better detection precision but also has satisfied dynamic response speed.