Abstract: The longitudinal weld and girth weld of 8 mm S30408 stainless steel storage tank were carried out by the combined welding method of DP-TIG and TIG with the welding material ER308 LSi. Through analyzing the weldability of S30408 tank body,designing the welding technology reasonably and controlling the key factors of welding strictly,the problem of weldability of 8 mm S30408 cryogenic storage tank was solved. According to relevant standards,the welded joints were tested for mechanical properties,X-ray detection and micro-metallographic analysis. The results show that the bending and stretching properties of welded joints meet the requirements of testing standards. The weld has no porosity,slag inclusion and other defects,and the ratio of austenite to ferrite in the weld is in accordance with the requirements. The combined welding method of DP-TIG and TIG is applicable to the welding of S30408 stainless steel.