Taking austenitic stainless steel Z2CND18-12（AC） used in nuclear power instrument tanks as the test object,the difference between automatic pulse TIG welding and GTAW welding is studied,including weld appearance in welding process and after welding,girth welding shrinkage,weld reinforcement and surface flatness,and the macroscopic metallography,microstructure and mechanical properties of welded joints. The results show that pulsed TIG welding has smaller welding shrinkage,better weld surface smoothness,more uniform weld microstructure distribution,smaller grain size,and better weld strength,plastic toughness and deformation resistance.