Abstract: The paper introduces the structure characteristics and design requirements of 1000 MWe nuclear power plant of improved second generation. Drawing welding and fabricating lessons of core barrel from domestic and overseas manufactory, combining the structure characteristics, stock option and design accuracy requirement, the paper put forward specific design and manufacture process measures to reduce welding deformation and control dimension precision on the base of theory analysis, requirement of ASME code and widespread experience in and aboard. Welding load and residual stress will be reduced largely and the manufacture difficulty and deformation risk also will be reduced through these measures.