The main pipeline of the nuclear power plant connects the pressure vessel,steam generator and main pump,and is the aorta of the nuclear power plant. At present,automatic all-position welding technology is used,and welding deformation is used for installation and adjustment of equipment during the welding process;aiming at the problem of excessive pump casing levelness and clearance of support leg gaskets caused in the repair process of the main pipeline of a nuclear power project,by adjusting the shrinkage and deformation during the automatic welding process of the main pipeline,the levelness of the pump casing,the support leg gasket,and the center position are finally adjusted to the requirements of the design standard, which ensures that the subsequent water conservancy components are installed in place,and provides reference and reference for follow-up similar issues.