Abstract: Central composite experimental design was used for the thickness of 0.4 mm TC2 titanium alloy in order to optimize the small scale spot welded joint quality. The welding current, electrode force and welding time were picked out as the process parameters and the nugget size, peak load, tensile shear displacement and failure energy were weighted into a welding quality comprehensive index based on entropy measurement method. The mathematical model between the welding quality comprehensive index and process parameters was obtained using regression analysis. The interaction effects of the welding parameters on welding quality were explored. The optimal combination of welding process parameters was achieved by using hill climbing method. The results of validation experiments showed that this study could effectively forecast and optimize the welding quality for the TC2 titanium alloy with the thickness of 0.4 mm.