A gas-assisted atomized liquid metering jet apparatus comprises a gas limiting hole, a jet hole, a liquid nozzle and a gas-liquid mixing cavity; the limiting hole is positioned at the upstream of the gas-liquid mixing cavity and connected with a compressed air source; and the jet hole is positioned at the downstream of the gas-liquid mixing cavity and communicated to an engine exhaust pipe. The gas-assisted atomized liquid metering jet apparatus is characterized in that the flow area rate of the limiting hole and the jet hole is less than 1, the gas reaches a critical state in the limiting hole, so that pressure in the mixing cavity remains stable relative to the engine exhaust pipe.