The Dongting Lake region is the transitional zone and important node between the Yangtze River Economic Belt and the South China Economic Circle, and its ecological security plays an important strategic role in the socioeconomic development of the Yangtze River Basin and even the whole country. Taking the city of Changde in the Dongting Lake as an example in this paper, the ecological security of the region is comprehensively evaluated, through the improved Pressure-State-Response model based on AHP and entropy weight method to determine the index weight, and the main factors of impacting ecological security are analyzed by grey relational grade method. The results show that: 1) the whole ecological security in Dongting Lake region has been improved, the level of ecological security has increased from the level ofless secure to more secure during 2013-2018, and the comprehensive index of ecological security has increased from 0.301 to 0.603. The pressure index of ecological security in this study region was slightly decreased, whereas the state index and the response index of ecological security increased. 2) The ecological security of Dongting Lake is mainly affected by industrial wastewater discharge, proportion of protected area, excellent rate of air quality index, population density and other factors. The main problems in Dongting Lake are water shortage, serious water pollution and unreasonable industrial structure. For further ecological security improvement in Donting Lake, it is suggested to follow the principle of harmony between human and nature and should control the wastewater discharge strictly, limit the scale of high-water-consumption industry, optimize the ecological security pattern, and explore the mechanisms and pathways to realize the value of ecological products for Dongting Lake wetlands.