The nuclear reactor pressure vessel（RPV）is the only non-replaceable core equipment in the nuclear power plant,which can withstand high temperature,high pressure and strong radiation. It has high design standards and specifications,difficult manufacturing process and strict quality control requirements.And the key welding technologies directly affect the quality and manufacturing schedule of the equipment,which is not only closely related to the economic benefits of nuclear power plant construction and operation,but also is the cornerstone of nuclear safety and even influences national security. In this article,by analyzing the characteristics of key welding technology and the typical quality problems of HPR1000 RPV,and by the research andoptimization and engineering practice of welding technology,the welding quality of HPR1000 RPV is significantly improved,meanwhile the time limit for a project is greatly shorten and the engineering cost is saved. This provides a valuable technical accumulation and engineering experience for subsequent manufacturing of HPR1000 RPV.