Aiming at the serious lack of rainfall-flood regime and safety monitoring, and the difficulty of hydrological forecast and risk assessment of reservoir safety in Guizhou Province, a supervision system is developed for the reservoir operation and safety monitoring of the whole province. Based on a Browser/Server architecture, the system used the WebGIS, GNSS and other technologies, and possesses both the functions of rainfall-flood forecasting and dam safety monitoring; with the collected history information and real-time data, the mining technology is pursued for further information identification and risk management. By providing the display modules of the overall function and typical projects, the system shows a strong performance for the dam safety monitoring and rainfall-flood forecasting ability, can facilitate the capability of flood forecast and disaster defense in Guizhou province, and thus provides technical support for the safe operation and intelligent management of reservoirs.