Abstract: Based on the idea of digital twin basin construction, this paper introduces the key technologies and specific applications of digital twin basin. The key technologies such as geospatial element collection of data base and sensing technology of Internet of things, multi- source heterogeneous data fusion technology, model base selection and general interface customization of the model platform, and bottom technology selection of the knowledge platform are briefly analyzed. Taking the pilot basin of the main stream of Qingshui River (the section from Chayuan Reservoir to Shidong Hydrological Station of Duyun City of Guizhou Province) as an example, the basin flood control system with the functions of "FEDE" of forecast, early-warning, drilling and emergency plan, and basin water resources management and allocation application construction are carried out, which provides a framework of thinking and case reference for the construction of digital twin basin.