Ecosystem health is one of the research hotspots in ecology. This paper discussed the concept of urban ecosystem health, and from the viewpoint of complex ecosystem, presented a new method and a calculation model for the comprehensive assessment of urban ecosystem health to overcome the current researches shortcomings. The application of the method and model in Foshan City of Guangdong Province showed that the assessment results could reflect not only the overall health status of the city, but also the relative health level of the city's sub-systems.