Urban lake is an important part of city wetland. With the continuous development of urbanization process, the demand for various resources of urban lakes has become increasingly strengthened. Based on the analysis of the characteristics of urban lake, the concept of urban lakes' health were put forward and the evaluation index system from the natural state of lakes and man - water relationships was constructed. Then 12 indexes to describe the urban lake ecosystem health were put forward, and the quantitative standard of each index was given. Qianlong Lake in Wu Jiang was used as an example for research. The results showed that, the comprehensive health index of Qianlong Lake in 2011 and 2014 were 0.343 and 0.582, respectively. It meant that Qianlong Lake had transformed from "micro pathological" to "sub-health" state. The ecological environment improvement of the lake was obvious, which showed that the index system had strong applicability,fully embodied the characteristics of the urban lakes. The evaluation results were objective and easily to extend. The assessment results showed that, the ecological restoration measures of Qianlong Lake was quite effective, so the Qianlong Lake ecological restoration system were arranged and supplied references for other urban lakes, it provided decision-making basis and experiences for the management of urban lake ecological system.