The invention provides a mixed diffuser with bypass gas bleeding. The mixed diffuser comprises an annular baffle achieving a diffusing effect. One end of the baffle is connected with a turbine rear engine case, and the other end of the baffle extends to the outer side of the position of an inlet of a thermal insulation screen. A gradually-expanding passageway is formed by the baffle and a turbinerear cone together. High-speed gas flowing out from the last stage of guide vane of a turbine is subjected to diffusion and speed reduction through the passageway. An annular gas bleeding and collecting cavity is formed by the baffle, the turbine rear engine case and a gas collection cavity barrel. The gas bleeding and collecting cavity communicates with a gas compressor through gas compressor gasbleeding pipes. One part of gas bled from the gas compressor enters the thermal insulation screen, and the other part of the gas flows through gas bleeding slits in the baffle and enters an afterburning chamber. A valve is arranged on each gas compressor gas bleeding pipe. The valves are closed in the turbine jet mode, and the valves are opened in the stamping mode. The mixed diffuser can work intwo work modes, namely, the turbine jet mode and the stamping mode, mode switching is supported, and variable cycle of an engine is achieved.