Abstract: Taguchi experimental design was utilized for the thickness of 0.4 mm TC2 titanium alloy with the purpose of optimizing the welded joint mechanical properties. The welding current, welding time and electrode force were selected as the significant process parameters and the nugget diameter, peak load; tensile shear displacement and failure energy were chosen to evaluate the qualities of the welding joints. The grey relational analysis was also employed to transform the four welding quality indexes into a gray comprehensive relational grade. The effects of the welding parameters on the welding quality were explored and the optimal combination of welding process parameters was achieved using range analysis of the experimental results. The results of validation experiments showed that this study could effectively optimize the small scale resistance spot welding quality for the titanium alloy with the thickness of 0.4 mm.