Constructed wetlands, as an ecological restoration technology,have been widely applied to deal with the degradation of natural wetlands and the pollution of water bodies, and more attention should be focused on the system stability and maintenance of functions over the long term. A Comprehensive Index System can be applied to perform an overall evaluation of an ecosystem through many different indices from different aspects and the Analytic Hierarchy Process is a structured technique for organizing and analyzing complex decisions particularly in group decision making. Based on the Comprehensive Index System and Analytic Hierarchy Process, we presented a measure method to evaluate the eco-sustainability of large-scale constructed wetlands,which are constructed for water purification and offsetting the degradation of natural wetlands. The index system contains three criteria: ecological structures and functions, water purification capability, and economic-social functions, and then fourteen sub-criteria including biodiversity, primary production, resistance to ecological invasion, wildlife habitats provision, COD removal, ammonia nitrogen removal, total nitrogen removal, total phosphorus removal, siltation, wetland plants harvest, operation costs, wetland plants benefits, recreation benefits and public awareness of the value of the wetlands. The weight of each criterion and sub-criterion is determined by the results of expert questionnaires. Five levels including "very good", "good", "average", "bad" and "very bad" are established to determine the sustainability of constructed wetland with the listed continuity intervals . A case study based on the index system was conducted in a five-stage surface-flow constructed wetland, which was built in the Xinxue River estuary by Nansi Lake to improve the water quality and to make up for the degradation of riparian wetlands. The calculated results of the weight of each criterion and sub criterion showed that "ecological structures and functions" and "water purification capability" account for 40.17% and 42.94% of the weight respectively, while biodiversity, ammonia nitrogen removal, resistance to ecological invasion, wildlife habitats provision, and COD removal are the main factors in the sub-criteria influencing the sustainability of the Xinxue River constructed wetland. According to the eco-sustainability evaluation, the eco-sustainability of the Xinxue River constructed wetland is at a 'good’ level (0.6862) on the whole, and specifically the ecological structure and functions (0.7732), water purification capability (0.6190) and social-economic functions (0.6492) are all at a 'good’ level, although the biodiversity index is 0.5200, which means the biodiversity of the Xinxue River constructed wetland is still lower than that of the natural wetland surrounding Nansi Lake, which also reflects the conflicts between ecosystem functions and structures in constructed wetlands. The index of benefits from the wetland plants is also in a "bad" level because the annual biomass of Xinxue River constructed wetland is kept in the wetland according to the local laws and regulations instead of being developed into commercial products. In conclusion, the further improvement for Xinxue River constructed wetland should focus on the extension of economic and social functions: development of wetland ecotourism should be exploited and the technological innovations of wetland plants processing should be enhanced to promote sustainable development of the local economy. The index system suggested here can also be adopted to evaluate other similar large-scale constructed wetlands.