Abstract: To meet the demand of the high efficiency power amplifier in microwave power transmission systems. A design method to improve the power-add efficiency and output power is proposed in this paper. Through the internal power flow statistics of the power amplifier, the influence of the feedback channel on the efficiency loss of the high-frequency power amplifier is analyzed, and then a feedback resonant network is introduced between the gate and the drain of the transistor to increase the impedance of the internal drain-to-gate feedback branch and to reduce the power loss of the internal of the transistor, resulting in the increasing of the power flow to the load while the total power generated remains the same, thus improving the power-add efficiency and output power of the power amplifier. The simulation results of the validation circuit show that the power-added efficiency is higher than 70%, and the drain efficiency is better than 80.5%, while the output power is higher than 10.5W in the frequency band of 5.78GHz~5.82GHz. It is proved that the proposed method is practical and feasible in improving the efficiency of power amplifiers, which will provide strong support for improving the efficiency of power amplifiers applied to the microwave power transmission systems.