Wudongde Hydropower Station Environment Information System which serves for the hydropower station exploitation is a comprehensive software system for environmental management and decision making. The system can integrate the basic geographical database, environmental database and attributive database on the basis of advanced ArcGIS Engine, Visual Basic, GIS spatial analysis function, environment evaluation modeling method and water quality model. It consists of two parts: querying system and decision making system. Querying system has several functions such as displaying, editing, querying，searching, spatial statistics, and spatial analysis. Decision making system sets the core modules. This paper describes the core modules of the software system in detail, including main researching contents and implementing processes of modules on ecological environmental qualitative evaluation, dynamic monitoring, environmental impact assessment, water pollution emergency prewarning. It is verified by application that this system reaches the design requirements wholly.