Abstract: As an important starting point to promote digital transformation and the rapid development of the digital economy, digital twin technology has been widely applied and has promoted the innovation and development of industries, such as manufacturing and smart city construction. However, limited by the randomness and complexity of the water system, the development of digital twin river is relatively limited. It has been mainly applied in flood management and damage reduction. According to the requirement on comprehensively mirroring and mapping the physical river and representing the full-process of the whole element of the river basin, there is still a long way to go. The gap lies at lack of data and acquisition techniques, modeling accuracy is not sufficient, and configuration technology for the construction of modules or process associated with the change of the physical world is not available. Thus, there is an urgent need to systematically carry out research on key technologies for the development of digital twin river. In this paper, the demands, concept, framework and key technologies of the development of digital twin river are discussed. In addition, taking flood management in Yangtze River as an example, the technologies of the construction of data-base, model library, intelligent application, and agile response configuration platform are presented. On this basis, in response to practical needs, methodology of knowledge-graph-based regulation rule-base and its application are developed; pilot studies at the Three Gorges Reservoir Area, the Han River Basin and the Lower Yangtze River Basin are carried out. The development program and technologies applied in the pilot studies can provide a valuable reference for future development of the digital twin river.