As an important part of the third barrier of nuclear safety, nuclear island steel lining is commonly pieced together by PC and PF shielded metal arc welding（SMAW） technology,which is the key and difficult point of quality control of nuclear island civil construction. The effects of different welding procedures and welding positions on chemical composition,microstructure and mechanical properties of welded joints are studied. The results provide a theoretical basis for the feasibility of the application of tungsten inert gas welding（TIG） in the nuclear island steel lining,which forms a whole set of new type welding procedures development ideas.