Abstract: In order to study the microstructure and mechanical properties of the weld metal of high nitrogen steel 1Cr22Mn16N, the steel was welded by CO₂ laser welding, and the influence of the shielding gas composition and heat input on the microstructure and mechanical properties of the weld metal was investigated. The experimental results indicate that the microstructure in the weld metal is austenite and δ-ferrite.The size of δ-ferrite is increased with the increase of heat input.The results also show that no soft zone occurs in the weld metal.The hardness of weld metal is increased as the heat input is decreased, and it is improved as N₂ in the shielding gas is increased.The toughness increases when the heat input decreases, whereas the compositions of shielding gas probably have no influence on the change of toughness of the weld metal.