In view of the problem that the input impedance does not match the RF internal resistance and the output power decreases due to the change of transmission distance or load in magnetic resonant coupling wireless power transmission system, an impedance matching method based on Smith chart theory was proposed taking L-type matching network as an example. Based on equivalent circuit theory and Smith chart theory, a parameter expression of matching inductance and matching capacitance is derived. In the case of impedance mismatch, the matching network parameters can be controlled by adjusting normalized resistance variables, so as to realize the impedance matching of the system. The simulation and experimental results show that the network structure of the matching method is simple and the complex computation process is avoided. Under the same conditions, the output power of the system after matching is significantly improved compared with that before matching, and the frequency splitting of the system can be effectively suppressed.