Abstract: In recent years, floods occur frequently in China, which poses a serious threat to the safety of people’s lives and property. To study and judge the flood situation in advance and reduce flood losses, according to the operational characteristics of flood and drought prevention and following the concepts of “four forecasts”, this paper puts forward an overall architecture of flood forecasting and control system based on “digital convergence - data backplane - twin platform - four pre-system”, and combs the business function and logic of the system. Based on the present situation of river system and flood control project in the Yongding River Basin, key technologies such as coupling simulation of hydrological hydrodynamic model and flood control operation model, real-time interaction between nested model and system data, and dynamic display of two- and three-dimensional geographic information are adopted, and a flood forecasting and control system of the Yongding River based on “four forecasts” is constructed to provide support for the flood dispatching decision-making of the Yongding River.