Abstract: The trend of the ecological security evolvement and the staged characteristics of Poyang Lake from 1980s to 2008was investigated, and the correlation between human activity and ecological security of Poyang Lake Basin, as well as the main factors influencing the lake's ecological security evolvement were explored deeply. The results indicated that the ecological security of Poyang Lake generally exhibited a declining trend, and had experienced three stages. A period with a rapid decline occurred from 1980s to 1990s, which was in the “very safe” state to the “safe” state. Due to the unreasonable mode of socio-economic development, especially since the large scale inning from 1950s to 1980s, the ecological security state rapidly declined during this period. A slow decline stage from 1990to 2002was in a “safe” state. After Poyang Lake was registered in the list of the key international wetlands in 1992and the application of “restoring lakes by stopping cultivation, population relocation” in 1998, the declining trend of the ecological security state slowed down. A period of the rebound stage was from 2003to 2008, which was close to the level of “general safety”. In 2003, the application of “Three Gorges Project” significantly changed the relationship between Poyang Lake and the Yangtze River. From that time, Poyang Lake Basin entered a new development stage, which resulted in the ecological security state coming into a rapid decline period. The unreasonable development model of economic and social is the important reason for the decline of the ecological security state of Poyang Lake. Over use of the resources of Poyang Lake by human directly worsens its ecological security evolution. There is a good linear correlation between the growth of population density in the region and the decline of its ecological security state of Poyang Lake. The reasonable population capacity of Poyang Lake region is 350people/km². Therefore, the conservation priorities and the harmonious relationship betwween human and lake are the key measures for the protection of ecological security of Poyang Lake.