Water-rich city not only has the general characteristics of urban water resources carrying capacity, but also has its certain particularity. According to the characteristics of the formation and utilization of urban water resources, the changes of urban water resources carrying capacity from 2006 to 2010 were analyzed by taking a water-rich city, Nanjing City, as a case, with comprehensive evaluation method. The results showed that the urban water resources carrying capacity of Nanjing City was rising on the whole, roughly in suitable load range, but the carrying capacity was limited with obviously fluctuation. The sensitivity analysis is applied to find out which indicators are the key factors for the changes of Nanjing urban water resources carrying capacity. On this basis, GDP per capita, water consumption per ten thousand Yuan GDP, urban daily water consumption per capita and the rate of sewage treatment are selected as four indicators for urban water resources carrying capacity promotion scenario analysis. It is find out, to strictly control the water consumption per ten thousand Yuan GDP and urban daily water consumption per capita, and steadily enhance the rate of sewage treatment, are very important to promote Nanjing urban water resources carrying capacity, and the corresponding countermeasures are put forward.