Taking＂Two Rivers and Two Stations＂engineering in the Chao Lake catchment as an example,the indicators and fuzzy cluster method for comprehensive environmental impact assessment of large-scale water conservancy engineering are discussed.The engineering effects to regional society,economy and eco-env ironment were analyzed according to the engineering location and characteristics,and to regional environmental background. Based on these, main effect factors were determined through field investigation,analogical analysis,expert consu-ltation and analytic hierarchy process.The compressive environmental impact assessment of the engineering was carried out by using fuzzy cluster analysis.