Abstract: With the ever-improving flood prevention engineering system of major rivers in our country, the prevention and control of flood disasters in small and medium basins has become one of the key contents of current flood prevention work. This article taking Lianshui Basin as an example,aims at the actual needs of hydrological characteristics, hydrological forecasting and flood dispatching of small and medium-sized river basins. Based on the coupled fine rainfall forecasting, comprehensive application of distributed hydrological model and reservoir dispatching model, a set of intelligent dispatching and decision support system for multi-reservoir in small and medium watersheds was developed. The system fully integrates technologies such as the Internet, WebGIS, water conservancy models,oblique photogrammetry and 3D virtual reality,adopts the current mainstream J2EE development framework,based on SpringBoot for front-end and back-end development and Restful service interface development, and realizes a good SOA service architecture, uses ElementUI, EChart, Maptalks etc. to achieve a good display interface for human-computer interaction.