Abstract: Dissimilar steel welding was carried out on SUS316L stainless steel and 15CrMo low-alloy steel by tungsten inert gas (TIG) welding with nickel base alloy welding wire ERNiCrMo-3 and stainless steel welding wire ER309. The microstructure and mechanical properties of the two welded joints were studied and compared. The results show that the solidification modes of the welds obtained with ERNiCrMo-3 and ER309 welding wires were austenitic and austenite-ferrite solidification modes, respectively, and the solidification structures were complete austenitic and mixed austenite-ferrite structures, respectively. Compared with using ER309 welding wire, using ERNiCrMo-3 welding wire could inhibit the diffusion of carbon in the welding process on 15CrMo steel side, and obtain a welded joint with higher tensile strength and percentage elongation after fracture. The peak hardness of the two welded joints appeared in the coarse-grained heat affected zone on 15CrMo steel side. Due to Laves phase in the weld obtained with ERNiCrMo-3 welding wire, the hardness was about 30 HV higher than that with ER309 welding wire.