Abstract: This project is a national key project, this paper describes in detail the welding and deformation control measures of the special large type beam with high strength and high lycium beam thickness used for the first time in China, starting from the design of the project scheme, a series of analysis and research were carried out, and specific technical measures were formulated and carried out in practice. The results show that the steel structure has little deformation, no cracks and 100% pass rate of weld. The successful experience of the project and the protective measures adopted in the limited space operation can be used for reference in the construction process of similar projects.