The upper shell is one of the key parts of the TVS-2 M high burn up nuclear fuel assembly using in Tianwan Nuclear Power Plant,which has the irreplaceable important function such as lifting fuel assembly,the control rods entrance,buffering and damping,ect. The upper shell has the characteristics of many components,complex structure,high requirements in dimensional accuracy and welding quality. The product production cycle,repair rate,rejection rate are high in the initial stage of localization trial production,resulting in serious process bottleneck. To ensure the quality of the product of nuclear reactor,it is necessary to study to grasp its core technology. The ultimate realization of manufacturing technology localization of the upper shell,to improve quality and reduce cost. In view of welding equipment modification,welding fixture design,productivity improvement,introduce the research work of manufacturing technical difficulties of automatic welding technology of the upper shell localization. The design of the research derivative has applied for 4 related utility model patents and been authorized.