Abstract: In order to understand the current situation of comprehensive ecological risk of water environment in Daning River Basin, the principal component analysis based on the information sensitivity was used to construct a water environment risk assessment index system, which can reflect the effects of risk source and receptor. We also evaluated the water environment risk and divided the risk level using GIS technology and relative risk assessment model under guidance of fuzzy evaluation thought. The results showed that: ① The ecological risk of water environment was mainly manifested in water eutrophication, soil heavy metals, soil erosion and water bloom. Fifteen evaluation indicators were finally determined by using quantitative screening method. ② The whole Daning River Basin was in a medium and high risk area. The risk value of the river basin showed a decreasing trend along both sides of the main river and tributaries. The high and extremely high risk areas were mainly distributed in Wuxi County and the estuary backwater area. The method overcame the subjectivity of the previous qualitative screening evaluation index and reduced the result’s uncertainty to some extent. The evaluation results objectively reflected the characteristics of population distribution, urban development along the river and the fact that water environment risk of reservoir tributaries were affected by reservoir impoundment, which provides a reference for the water environment risk assessment and control of other tributaries in the reservoir area.