Abstract: In the advanced semiconductor process, it is necessary to precisely control the plasma ionization rate and ion impact energy, and the traditional single-frequency power supply makes it difficult to achieve the above goals, so a dual-frequency is proposed. It is of great significance to develop dual frequency matchers in order to achieve impedance matching at different frequencies. This article designs a dual frequency automatic impedance matcher based on a diode amplitude-phase detection circuit. Simulation research shows that Urms can represent the matching degree between the RF power and the chamber; the greater the Urms, the greater the degree of mismatch, and vice versa, the better the matching degree. Gama and T-type matching networks are used for matching outputs of 13.56 M and 400 kHz signals, respectively. Simulation results show that the structure exhibits excellent transmission characteristics, with a theoretical insertion loss of less than −0.002 dB and high isolation, with a theoretical isolation of −34.4 dB. The optimization algorithm has the characteristics of fast response and high matching accuracy, and uses this method to achieve impedance matching between the RF source and the chamber.