In order to dispatch the excessive extreme flood and ensure the flood control safety, the early warning model for water areas exceeding the alarming and guaranteed level based on the coupled hydrology and hydrodynamic models, and the rapid assessment model of flood risk based on the hydrological method. The models and the system were intelligently interacted in the forecasting and dispatching integration system of the Taihu Lake Basin, to realize the visualization of forecasting and scheduling results. Based on the National Water One Map System, the dynamic demonstration of water exceeding the alarming and guaranteed level, with the risk assessments of flood inundation, achieved the product breakthroughs from station forecasting to area prediction, from conventional forecasting to impacting prediction, as well as the flood risk from static evaluation to real time dynamic assessment. The system has been applied in resisting the 2020 major flood in the Taihu Lake Basin. The results showed that 39 risk reminders of water exceeding the alarming and guaranteed level, as well as 4 risk assessments of flood inundation, were released by the Bureau of Hydrology Information Center of Taihu Lake Basin Authority. The forecasting results were consistent with the observation, provided technical support for the dispatching, and avoided more than 30 thousand people evacuation in Suzhou city of Jiangsu Province, which guaranted the safety of flood control in the Taihu Lake Basin.