Abstract: According to eco-environmental characteristics of longitudinal range-gorge region in Yunnan Province, China, an appraisal indicators system of ecological security was established by the analytic hierarchy process method. Based on this system, the comprehensive index method and gray correlation theory were applied to appraise the ecological security state and analyze the key factors of ecological security of the region. The results show that the ecological security state in the region as a whole is good. Main factors which affect ecological security are vegetation overcast rate, population natural growth rate, water quantity change, industry structure, population diathesis, soil losing rate, and exploiture land rate. There are different ecological states in different regions and drainage areas, and the ecological states of west region and Nujiang drainage area are the best. Different measures should be taken to manage eco-environment in the region so as to protect the coordination development of natural, economic and ecological environment.