In recent years, it has been very important for regional sustainable development to valuate the degree of regional ecological security with regard to resource depletion objectively and to analyze its influential factors. This paper tries to assess the ecological security in Chongqing while investigation the main factors. The caculations of consumption footprint, production footpring and ecological capacity in Chongqing from 1996 to 2007 based on ecological footprint approach were carried out. Further, ecological security index was calculated by researching the results above and the factors influencing ecological security were analyzed with factor analysis methed. The results indicate that both consumption footprint and production fooprint present an upward trend in the study, contrary to the gradually decreasing trend of ecologic capacity. In addition, the ecological security index calculated shows that the ecological security of Chongqing has deteriored from a level of less risky to that of risky. The findings of factor analysis suggest that the deterioration of ecological security in Chongqing shall be ascribed primarilty to socioeconomic factor and industrialization. With socioeconomic development and industrialization process, appropriate measures must be taken to improve the ecosystem in Chongqing, so as to achive sustainable developmen. In the end, the limitations of this study were also discussed and the areas that requie further research were presented.