Abstract: The digital twin watershed is an important part of the digital twin earth. Clarifying the theoretical definition and connotation of the digital twin watershed is the premise and foundation for the research and construction of the digital twin watershed, and it is of great significance for the intelligent management of the watershed. Based on the digital twin theory and technology, the following research has been carried out in this paper. ① The definition of a digital twin watershed is given, and it is considered that a digital twin watershed is a new infrastructure and new paradigm serving the entire life-cycle management of the watershed, which is the interactive mapping, co-intelligence evolution, and virtual reality integration between physical and virtual watersheds driven by the full amount of data and domain knowledge, and the differences between a digital twin watershed and traditional modeling and simulation are analyzed. ② The connotation of a digital twin watershed is to realize the full life-cycle control of physical watershed objects by loading the physical watershed into the virtual watershed, mapping the physical watershed with the virtual watershed, and then managing and controlling the physical watershed using the virtual watershed. Its characteristics include high fidelity, evolution autonomy, real-time synchronization, closed-loop interaction, and symbiotic evolution. ③ The basic model of a digital twin watershed is composed of a physical watershed, a virtual watershed, the real-time connection and interaction, the digital enabling service, the twin watershed data, and the twin watershed knowledge. Its core capabilities include physical watershed perception and control, digital expression of all of the water-related elements, visual dynamic presentation of real scene, watershed data fusion supply, watershed knowledge fusion supply, watershed simulation and deduction, and self-learning and optimization of digital twin watershed. ④ This paper puts forward the key scientific problems and key technical systems to be solved in the digital twin watershed, and looks forward to the development direction of the digital twin watershed from the perspective of a perception network, data network, knowledge network, model network, and service network, and expounds the enabling field of the digital twin watershed. This paper aims to provide theoretical guidance for the application of digital twin watershed technology through the new research paradigm of digital twin watershed theory and to provide useful inspiration and reference for future smart watershed research and the application of digital technology in watershed governance and management.