A power amplifier circuit based on envelope tracking technology and Doherty architecture and a design method thereof, the circuit comprises a Doherty architecture and an external power supply; the external power supply is an ET power supply or an APT power supply; an output terminal of the ET power supply or APT power supply is connected to a drain electrode of a first transistor in the Doherty architecture; or the output terminal of the ET power supply or APT power supply is simultaneously connected to the drain electrodes of the first and second transistors in the Doherty architecture. The circuit makes a power amplifier work in the saturation state and therefore effectively improves the efficiency at the output power.