Abstract: In view of problem that current impedance matching methods ca't automatically adjust load impedance of magnetic resonant wireless power transfer system(MR-WPT) when load changes, which leads to reduction of energy transfer efficiency of the system, a load adaptive impedance matching method of MR-WPT system was proposed. In order to improve power transmission efficiency of MR-WPT system by using high frequency, class E power amplifier is used as high frequency inverter circuit. A DC/DC converter is added between magnetic resonance device and load. When the load impedance changes, the load resistance is transformed to the maximum efficiency transmission resistance by adjusting the duty cycle of the DC/DC converter, thus ensuring that the MR-WPT system always works at maximum efficiency. The simulation and experimental results show that the proposed impedance matching method is feasible and can optimize transmission efficiency of MR-WPT system. When the output power is 3.5 W, the transmission efficiency reaches 35%.