The invention provides a coal gas generator which comprises a shell and a reaction chamber arranged in the shell, wherein the reaction chamber is a hollow cylinder with two open ends, and the hollow cylinder is formed by a membrane water-cooling wall; a first burner casing and a plurality of second burner casings, which communicate with the hollow cylinder, penetrate through the top end of the shell; and the second burner casings are annularly arranged on the top end of the shell around the first burner casing. The coal gas generator provided by the invention solves the technical problems of poor adaptability to technological design conditions and lower adjusting capability for technical operation load in the existing coal gas generator.