Abstract: 3 mm thick 304 L austenitic stainless steel plates were welded by Friction Stir Welding（FSW） and Tungsten Inert-Gas Welding（TIG） respectively, then the microstructure and tensile properties of the welding joints of the two different types of welding were compared and analyzed. The results of the comparison and the analysis show that the FSW welding joint microstructures is composed of four regions, welded nugget zone, thermal-mechanically affected zone（TMAZ）, heat affected zone（HAZ）, and shoulder affected zone（SAZ）. And the microstructure in the nugget is uniform fine-scale equiaxed recrystallisation grain, and the materials in TMAZ underwent plastic deformation, but the materials in HAZ just underwent heat effect. The TIG nugget includes cellular dendrite austenitic, lath ferrite or vermicular ferrite. The tensile properties of FSW joints is the same as those of the TIG joints, and both of the tensile properties of the two types of welding joints are slightly higher than those of the base materials of the welding joints.