Abstract: Taking the Φ45 mm×8 mm austenitic 304 stainless steel pipe as the subject of study，the butt welding process applying A-TIG welding technology（argon tungsten arc welding with activating flux）is tested.The effects of different welding starting points on the formation of welds are studied，and the performances and microstructures of welding parts with satisfied appearance quality are tested.The analysis result shows that when A-TIG welding technology is applied on the Φ45 mm×8 mm austenitic 304 stainless steel pipe，the full welding penetration at one time and the double-sided formation by single-side welding are realized without bevelling or using of filler wire.The weld is of austenitic+ferritic structure，and although it is consistent with that of the weld when no activating flux being used，the adding of activating flux is able to significantly improve the structure performances.The perfomances of the weld joint is in compliance with applicable standard.