Abstract: Objective The aim is to address the welding process challenges of 304 and 3Cr13 dissimilar stainless steels with different thicknesses, and to meet the engineering application requirements for dissimilar alloy welding in related fields. Methods Galvanometer-scanned laser welding of 3Cr13 martensitic stainless steel and 304 stainless steel with different thicknesses is carried out using different scanning speeds and laser powers. The properties of the welded joints are analyzed by testing methods such as tensile strength, elongation after fracture and hardness, as well as by characterization methods such as macro morphology and microstructure of joints. Results The welded joints with better performance are successfully obtained under appropriate galvanometer-scanning laser welding parameters. The microstructure of welds is mainly composed of martensite, with large differences in the size of heat affected zone, but not much difference in the microstructure morphology. Relative to the scanning speed, the laser power has a more obvious effect on the tensile strength of the welded joints, and when the laser power is 2 400 W, the tensile strength reaches a maximum value of 705 MPa, which is between two base materials and reaches 96% of the 3Cr13 martensitic stainless steel. Fracture tends to occur on the thinner 304 stainless steel side. The maximum hardness of welded joints reached 574.2 HV0.3. Conclusion Galvanometer-scanned laser welding can successfully realize the effective welding of 304 and 3Cr13 stainless steels with different thicknesses. Rational regulation of laser power can significantly improve the mechanical properties of welded joints, and this welding process is suitable for the welding fabrication of such dissimilar stainless steels.