Abstract: TA1 titanium sheet and SUS304 stainless steel sheet were welded by resistance spot welding with 100 μm thick NiCr alloy as the interlayer. The microstructure characteristics of the joint were observed and analyzed. The effects of welding process parameters on the nugget diameter and shear force of the joint were studied. The results show that the reaction layer with 50 μm thickness consisting of α-Ti and Ti₂Ni was formed near titanium side at steel/titanium interface outside nugget zone. The reaction layer with 15 μm thickness consisting of α-Ti and TiFe was formed between titanium and nugget; the reaction layer with 7 μm thickness consisting of Fe and TiFe₂ between stainless steel and nugget; the center of nugget region was composed of mixtures of TiFe and TiFe₂. The nugget diameter of the joint increased with welding current and welding time, and decreased slightly with the increase of electrode force. The shear force of the joint increased and then decreased with the increase of welding current, welding time and electrode force. All joints were torn at the bonding interface after shear tests.