Abstract.As the main power source, the stable supply of energy is important for urban sustainable development. It is necessary to systematically evaluate the security level of urban energy supply, based on which the key influencing factors can be investigated and then the energy supply security can be improved. Ecological network analysis, a helpful systematic analysis tool, was introduced to evaluate the level of urban energy supply security, with the merit of connecting different components within a holistic network system. Such indicators as system sustainability and weights of different components were calculated to analyze the characteristics of energy supply system based on information and structure analysis. The established model and indicators based on ecological network analysis were applied by choosing the natural gas supply system in Chongqing city as the case. The results show that the level of natural gas supply security in Chongqing generally increased during 1997-2012. And the natural gas production sector, consumption sector, and domestic suppliers outside the city caused greater impact on the natural gas supply system than other components during the study period. Based on a few scenario analysis, certian suggestions were put forward to improve the security level of natual gas supply in Chongqing.