Abstract: The paper introduces the basic constitution of containment steel liner to Pakistan Chashma nuclear power plant (C-2) project,and analyses the origin for the endless crack in the welding joints of SAW.To prevent occurring of endless cracks in SAW,well match of the main welding parameters is the base way to eliminate the weld of big reinforcement and small width.Correct chose and reuse of granular of welding flux is important for reducing of the blowhole and pit on weld surface.Secondary cutting can mitigate the deformation of the whole plate after welding.