Abstract: 2mm thick X2CrNiN18-7 stainless steel is used to carry out a comparative experimental study of CMT welding and MAG welding process. Mainly from the weld shaping, joint metallurgy, mechanical properties, welding spatter and welding deformation, etc. Comparative analysis of stainless steel CMT welding process and MAG welding process differences. The results show that the weld of the two welding methods are typical melting electrode gas shielded weld seam forming, and the two main organizational components are austenite-based, and a small amount of ferrite. Due to the high heat input of MAG welding, its characteristic area than the CMT welding lack of part of the melting zone and isometric crystal area, CMT welding weld strength and elongation is higher than the MAG welding, welding spatter is only about 20% of the MAG welding, and the same kind of external conditions under the same type of joint optimization process CMT welding deformation is smaller than the MAG welding, the maximum weld deformation of about 70% of the MAG welding.