Abstract: There are not yet a common view and sysmatical data on the problems of the grain boundary corrosion during welding ferritic staiuless steel at present. This article deeply discusses the phenomenon of ferritic stainless steel grain boundary corrosion,the sensitization of ferritic stainless steel,the theories on the grain boundary corrosion,the affections of elemental compositions and corrosion mediums,and attention points in welding.