The invention discloses a supersonic gas ejector. The supersonic gas ejector comprise a gas inlet barrel, a fuel nozzle, an igniter, an ejector housing, a combustion device and a diffusion device, wherein the ejector housing sleeves the outer surface of the air inlet barrel, and a cavity is formed between the ejector housing and the air inlet barrel; the combustion device is arranged in the cavity; the combustion device comprises a combustion barrel and a spray tube; the igniter is connected to the combustion barrel through the ejector housing; the spray tube is connected to the back end of the combustion barrel; and the diffusion device is connected to one end of the ejector housing. The device disclosed by the invention employing high-temperature gas expansion is high in thermal efficiency, suitable for long-term operation, simple in structure, easy to process and low in manufacturing cost.