Abstract: In order to ensure the water environmental safety in the Three Gorges Reservoir Region and improve the early environmental warning and emergency handling ability, a system was developed with functions including risk prevention, monitoring and emergency treatment. The present study addressed the demands of environmental risk management and emergency handling in Chongqing City, utilized the idea of “combining routine monitoring with emergency response,” and presented a Service-Oriented Architecture, Webservice-based data calling mode and function modules platform technology. By integrating the operation system achievement of the local environmental protection bureau, an innovative system of water environmental risk assessment and early warning, called the “five unified into one” system, including one system, one network, one map, one table and one process, was designed and developed. The system realized the function of potential pollution source risk identification, environmental early-warning monitoring, simulation, emergency assessment disposal and information publishing, and was applied in the environmental protection department in Chongqing City. The results supported the emergency management and daily management. In a series of unexpected events to verify the business application, environmental emergency response time was shortened from 1-2 hours to 10-20 minutes, and the emergency response time was shortened from the original 1-2 days to 1-2 hours. The system improved water environment risk assessment, early warning and prevention ability in the Three Gorges Reservoir area, and provides a reference water environmental control for other districts in the whole country.