With rapid modernization of big cities, increasingly more problems have been found in urban flood control management and decision-making. Thus it is necessary to introduce SDSS theory and technology in order to optimize decision-making process. Based on characteristics of Shanghai flood control, and integrated with hydrology, meteorology, geomorphology, Geographic Information System, model database and knowledge database, a flood control SDSS was designed for the purpose of real-time monitoring and forecasting. Depending on the system, flood control departments can make scientific and reasonable decisions, and realize the objective of bringing flood control into modern administration.