Abstract: The in-depth coupling of hydrological monitoring and forecasting with urban flood disaster monitoring and early warning is crucial for improving the urban flood defense capabilities. Through a detailed analysis of the successful cases of Shanghai's "Integrated Management through One Network" in flood control and Wuhan's "Smart Water Affairs" construction, it systematically researches the internal logic, practical approaches, and development directions of the in-depth coupling between hydrological "Four Prerequisites" (Forecasting, Predicting, Pre-simulation, Pre-arranged plan) and urban flood defense. Currently, there are four common obstacles in the coupling of hydrological forecasting and predicting with urban flood monitoring and predicting: inefficient cross-departmental information sharing, a lack of connection between hydrological and urban waterlogging models, ineffective linkage between predicting and response, and a mismatch between technology and its application. To address these issues, it proposes a coupling system. This system is founded on the integrated integration of data, centered around the integrated drive of models, facilitated by the integrated coordination of operations, and targeted at the deep integration of technology and application.