Abstract: Digital twin technology, as the core engine driving the new stage of high-quality water conservancy development, holds strategic significance for enhancing the modernization level of the Changjiang River Basin governance. By analyzing the foundation of digital twin Changjiang River construction, and based on the current critical transition from pilot demonstrations to systematic construction, this study proposes a systematic top-level design framework encompassing consolidating infrastructure, building a twin platform, deepening business applications, and improving support guarantees. The framework also formulates the "two-step" construction goal, which involves laying a solid foundation and enhancing capabilities to build the digital twin Changjiang River 1.0 by 2027, and iterative optimization to build the digital twin Changjiang River 2.0 by 2030. Furthermore, implementation guarantee strategies are puts forward from four dimensions: project coordination, task division, standard specification, and organizational support. The research findings can guide and promote the digital twin Changjiang River from top-level design to implementation.