The invention discloses a power amplifier comprising a frequency difference computing unit, a first phase different computing unit, a regulating unit and an amplifying unit. The frequency difference computing unit is used for computing frequency difference between a single-frequency reference signal and an input signal of the power amplifier; the first phase different computing unit is used for computing phase difference between the single-frequency reference signal and the input signal of the power amplifier; the regulating unit comprises a subunit used for regulating power of the input signal of the power amplifier according to a first control signal based on the frequency difference and a subunit used for regulating phase of input signal of the power amplifier according to a second control signal based on the phase difference; the amplifying unit is used for amplifying an output signal of the regulating unit to obtain an output signal of the power amplifier. By the power amplifier, the problem of output waveform distortion caused by nonlinearity of frequency response of a regulating unit in the power amplifier is solved, and output waveform distortion caused by junction temperature change and capacitance pool discharge can be eliminated.