Abstract: In order to achieve the goal of protecting the environment of the Yangtze River Economic Belt, it is urgent to implement the water quality target management. According to the concept of 'classifying, zoning, grading and staging', based on the technology of basin water quality target management, a mathematical model of unsteady water quantity and quality in typical downstream regions of the Yangtze River Economic Belt was established by combining one-dimensional and two-dimensional models. In this study, 10% of the Yangtze River shoreline length was selected as the largest pollutant discharging zone within which the cross-section water qualities conformed to the regulations. Based on the calculation results that obtained by generalizing discharge amounts of outfalls, the environmental capacities of 90 water environmental function zones along the main stream were analyzed. The results indicate that in eight cities, the regional total discharge control values of COD, ammonia nitrogen and TP were: 59, 537, 8, 099 and 1, 008 t/a in Nanjing, 26, 830, 2, 668 and 356 t/a in Yangzhou, 44, 683, 3, 344 and 480 t/a in Zhenjiang, 36, 919, 2, 598 and 388 t/a in Taizhou, 6, 689, 538 and 76 t/a in Changzhou, 831, 121 and 15 t/a in Wuxi, 42, 384, 4, 365 and 546 t/a in Suzhou, and 32, 893, 2, 986 and 382 t/a in Nantong, respectively. According to the survey, Nanjing had the highest capacities of COD, ammonia nitrogen and TP, while Wuxi had the lowest capacities. The research can provide a scientific basis for policy and decision-making on pollutant loading reduction and pollutant emission control in cities along the Yangzi River.