Problems in the management of medium-sized and small hydropower systems are analyzed， and the general design scheme of developing medium-sized and small hydropower management systems based on the MVC model by adopting the Rich Internet Application（RIA） technology is put forward. The developing target， main framework， and function structure of the system are discussed with emphasis on the key techniques in the design and realization of the management system. A medium-sized and small hydropower management system is designed and developed based on the RIA technologies and is successfully applied to the management of medium-sized and small hydropower in Yunnan Province. Actual operation results show that the hydropower management system based on RIA under discussion can significantly improve the management efficiency and enhance the automation level of power dispatching.