In order to strengthen the flood risk management of Hongze Lake area and ensure the flood control safety of the lower reaches of Huaihe, by combining WebGIS with hydrology and hydrodynamic model, a 1D-2D coupled hydrodynamic model is embedded into the B/S system to forecast and warn flood. A 1D river, 2D lake and detention basin coupled flood routing model was built, on this basis, the flood forecasting and warning system of the Hongze Lake area is developed based on WebGIS. The rainfall and flood can be real-time monitored and forecasted, the water level and flow changes at the concerns, with the flood risk and over-level flood warning information can be visualized. The system further improved the digital level of flood control of the Hongze Lake area, and can provide decision support for emergency escape and disaster reduction.