Abstract: A series-parallel resonant matching circuits and a broadband power amplifier thereof are disclosed. The series-parallel resonant matching circuit is connected to the last power transistor and the next power transistor. The series-parallel resonant matching circuit comprises a series matching inductor, a parallel matching inductor and an impedance transformation unit. The impedance transformation unit is connected between the series matching inductor and the intrinsic parallel matching inductor for transforming impedance. The parallel matching inductor and the parallel capacitor of a last level power transistor constitute a LC parallel resonant circuit, the series matching inductor and the series intrinsic capacitor of a next level power transistor constitute a LC series resonant circuit. Besides, the intrinsic parallel capacitance is a drain-to-source capacitor for the power transistor. The intrinsic series capacitance is a gate-to-source capacitor for the power transistor.