The present invention proposes a composite mechanism full-flow cycle supersonic propulsion system and its working method, including an air inlet, a compressor, a diffuser duct, a shaft, an open pre-combustion driver, a closed pre-combustion driver, a turbine, a post-combustion Thruster, tail nozzle; the inlet, compressor, shaft, turbine, afterburning thruster, and tail nozzle are connected in sequence; the compressor and turbine are connected through a shaft; the turbine is located on the side of the inlet of the afterburning thruster, The tail nozzle communicates with the outlet of the afterburner thruster; the open pre-combustion driver and the closed pre-combustion driver are located behind the compressor, and the outlet is facing the turbine; the open pre-combustion driver and the closed pre-combustion driver are alternately distributed on the outer ring of the shaft Into the expansion duct of the space. The system maximizes the propulsion advantages of each subsystem in terms of specific impulse and thrust-to-weight ratio, so as to realize the rapid self-starting of the propulsion system, multi-degree-of-freedom, compound working mechanism, efficient and economical supersonic combined propulsion system.