At present,ecological safety problem of the Chaohu Lake Basin is very serious,hindering the sustainable development of society and economy.We proposed the Chaohu Lake Basin ecological security assessment framework model and index system based on water environment and water ecology by using the data of society and economy,water environmental quality and aquatic ecosystems in the Chaohu Lake Basin,and applying driving force-pressure-state-impact-response(DPSIR) model.We also assessed ecological security of the Chaohu Lake by using fuzzy entropy matter-element evaluation method.The results show that overall,the Chaohu Lake Basin is in a moderate risk status of ecological safety in 2003 and 2007;the changes of water quality of the environment and aquatic ecosystem were a serious threat to the basin ecological security;the TP concentration,NH₃-N concentration and TN concentration in water were the most critical factors determining ecological security of the Chaohu Lake Basin.