The invention provides a gas production method and device. Powdered coal, first water vapor and oxygen-enriched air are added to a gasifier, the powdered coal conducts an incomplete combustion reaction with the oxygen-enriched air and conducts a first gasification reaction with the overheated water vapor at the high-temperature environment, and first gas is generated, wherein the first gas contains the unreacted powdered coal. Second water vapor is added to an outlet in the bottom of the gasifier, the first gas moves downwards to the outlet in the bottom of the gasifier to conduct a second gasification reaction with the second water vapor, and second gas is generated. The second gas enters a heat exchange cooling device to be cooled, and gas is obtained. Carbon conversion efficiency is improved, waste heat in the first gas is consumed, heat loads needing to be treated by the follow-up heat exchange cooling device are reduced, and therefore high-temperature erosion corrosion of gas backflow to the wall of the heat exchange cooling device is relieved.