In order to meet the requirements of the high efficiency for the wireless communication system, this paper introduces a high efficiency power amplifier (PA) based on the harmonic control technique. Compared with other works, this method can realize the second and third-harmonic impedance matching accurately. Besides, to avoid the problem of transmission line with high characteristic impedance in bias network, the π-typed and L-typed structure is utilized. For demonstration, a high efficient PA using CGH40010 GaN HEMT is designed and fabricated. The measured results show that it obtained an output power (Pout) of 39.5 ± 1 dBm, a Gain of 14.5 ± 1 dB, a maximum drain efficiency (DE) of 74.6% within the frequency range of 0.3–1.75 GHz. After comparison, this PA is superior in terms of efficiency and gain and has predominant engineer application.