Combined with the construction case of the large-span circular steel box girder structure at the visitor reception center of Cuiping Mountain Scenic Area in Yibin City, the principle of high-precision assembly technology and key technical points of large-span circular steel box girders were introduced.3D modeling was used to assist in the factory processing of circular steel box girders, the design and installation of temporary support frames, the precise control of steel box girder hoisting and positioning through BIM (building information modeling) technology in conjunction with total station instruments, and the information-based monitoring of the welding process. These key technological processes have been implemented in the project, which not only shortened the construction period and saved costs but also greatly improved the installation accuracy. This has made the overall assembly of the steel box girder structure smoother and the visual effect of the shape better.