Abstract: Objective The aim is to investigate influence of single-side and double-side welding on mechanical properties of single-side crmpexed T-joints. Methods MAG (Metal active gas arc) welding method is utilized to weld single-side crimped T-joints of SUS304 austenitic stainless steel with single-side and double-side welding, and 308L Si stainless steel is selected as welding wire. The solidification and crystallization modes metal of welded joints in the welding process are discussed and analyzed, as well as microstructure and mechanical properties. Moreover, stress and strain of welded joints under tensile state are analyzed by finite element method. Results By utilizing MAG welding of SUS304 austenitic stainless steel, welded joints with excellent properties can be obtained, and solidification modes of different areas of weld joints are not affected by welding passes. Conclusion Due to change of temperature gradient and element segregation, solidification modes of WM (Weld metal), FZ (Fusion zone) and PMZ (Partially molten zone) are FA (Ferritic-austenitic), FA/F (Ferritic) and AF (Austenitic-ferritic) modes, respectively. The microstructures of WM and PMZ of welded joints are mainly composed of columnar austenite and lathy ferrite, and microstructure of FZ acicular ferrite. The tensile strengths of welded joints obtained by single-side welding and double-side welding are almost equal to that of BM, however, tensile stress is concentrated in different areas, thus resulting that single-side welded joints tend to concentrate at FZ, while double-side welded joints are prone to concentrate at BM.