Abstract: As a result of basin digital mapping, 3D data baseboard is the basis of digital scene construction and intelligent simulation iteration.In order to clarify the technical logic, this article systematically elaborates on the positioning, construction tasks, and technical roadmap of the 3D data Baseboard.We elaborate key technologies such as massive data fusion, lightweight data processing, scene rendering and publishing, data visualization and calculation, and data sharing and co construction during the construction process, during which we focus on the technical difficulties, solutions, and specific methods.Based on the above research, taking Cao′e River digital twin basin as an example, we construct 3D data baseboard( L2 and L3) based on BIM+GIS and other technologies, and use 3D digital scenes to support the application of visualization models such as "four presets" in the basin.The results have reference significance for similar data baseboard construction.