Abstract: The RS monitoring and risk evaluating system for flood hazard is based on GIS and RS technology. This relatively integrated system comprises flood information receiving and collection, flood simulation and hazard loss. By the integration of database and model-base, the system receives and collects up-to-date information about flood from RS monitoring and routine observation. In application of image processing and information amalgamation, we can rapidly confim the distribution of flood situation spatially and temporally, report the submerged area and estimate economical loss in time, and provide scientific methods to experts for them to manage, decide and command rescue in their disaster-resisting work.