By developing an evaluation index system and applying of analytic hierarchy process(AHP)comprehensive evaluation,an ecological risk assess-ment of the ecosystems in the Shitoukoumen Reservoir basin was carried out with considerations of natural conditions and human disturbance of the study area.Based on historical documents and field survey,three factors including point source pollution,non-point source pollution and drought were selected as risk sources.The results show that ecological risks of the basin displayed substantial spatial variability.The key ecological risk sources were total nitrogen and phosphorus in the water,with weight coefficients of 0.2247and0.1945,respectively.The results of this study provided quantitatively a theoretic basis and data support for the environmental management and ecological risk decisionmaking.