The invention provides an RF power amplifier with post-distortion linearizer. The power amplifier includes a main amplifier, an auxiliary amplifier and a phase compensator. The first amplifier has a first input end and a first output end and operates in class A or AB. The auxiliary amplifier has a second input end and a second output end and operates in class B or C. The second output end connects the first output end to form a signal output end. The phase compensator has a third input end and a third output end and compensates a phase difference between the main and auxiliary amplifiers to make outputs of the two amplifiers opposite in phase. The third output end connects the second input end. The third input end connects the first input end to form a signal input end.