Abstract: In recent years, with the rapid advancement of water conservancy informatization, the theory of digital river basin has received more and more attention, and the design and implementation of river basin simulation platforms have gradually become an important part of it. GIS applications under the traditional C/S architecture are difficult to meet the current cross-platform, lightweight, scalable and remote application needs of water conservancy informatization, while WebGIS technology can effectively deal with the above problems, but massive spatial data and limited bandwidth make it restricted in engineering applications. By adopting a simulation mode of key elements of river basin, such as reservoirs and river channels in water resources management, we build a client-side lightweight WebGIS platform. We study the development ways of river basin simulation information system, and analyze and expound the business application with WebGIS in the whole scene simulation of river basin under the B/S architecture system in detail. Furthermore, we provide a solution for the multi-condition real-time simulation of water resources management. The design system of the platform had applied in the water resources management decision support system for the lower Jinsha River-Three Gorges cascade dispatching of the Yangtze River, and had achieved a good simulation integration effect.