A typhoon decision-making support system,which has been put to use in Zhoushan,is described. Based on a large number of meteorological and hydrological data,real-time observations,and important information about flood-prevention facilities in Zhoushan,a typhoon composite database is established. Through the system,the similar typhoon can be found by searching for the database when a typhoon approach. Its final report can help the government prevent and resist typhoons,to reduce loss effectively.