The utility model provides a self -adaptation biasing RF power amplifier, it includes: front end power amplifier carries out front end power amplification to radio frequency incoming signal, intermediate power amplifier carries out centre power amplification to radiofrequency signal, sampling circuit is right the radiofrequency signal after the front end enlargies of front end power amplifier output carries out voltage sample and obtains sample voltage, rectifier circuit will sample voltage converts the DC voltage to, the low pass filter circuit, it is right the DC voltage carries out low pass filter, voltage current conversion circuit will pass through behind the low pass filter the DC voltage changes direct current into and does intermediate power amplifier's output provides bias current, a field effect transistor accepts the radiofrequency signal behind middle power amplification, and is right radiofrequency signal enlargies with output radio frequency output signal. The utility model provides a self -adaptation biasing RF power amplifier's the direct watt level based on radio frequency incoming signal of gain carries out dynamic adjustment.