Abstract: The amount of domestic sewage discharge in Chinese cities in 2020 was projected by integrating systems analysis and mode-forecast methods, based on the statistic data on domestic water and domestic sewage as well as data on their variation trend, variation rules and annual variation amounts from 1985 to 2003. Three kinds of projection were made, including warning projection, rolling projection and circular economy development projection. The projected domestic sewage discharge for these three cases are respectively 40.24, 35.54 and 17.35 billion t. By comparative analysis, the circular economy development projection result, 17.35 billion t, was recommended as the final projection amount. The Green GDP index of freshwater resource was proposed, and a case study in one city carried out with the estimation of its freshwater resource wealth.