As the vital step of knowledge discovery,data mining is the process of getting the unknown,valuable and operable information to utilize for decision-support.There are a lot of hydrological data in the departments of flood control in China.How to fully use all kinds of intelligent algorithms to analysis and mine these data to get useful information is one of important aspects for development of the Flood Control Decision-Support System(FCDSS).After all-around introducing the architecture of data mining technology and the architecture of hydrological forecasting based data mining,this paper discussed application of data mining technology in hydrological forecasting.