To carry out the demonstration of setting up the sewage outlet into the river of the urban sewage treatment plant in the urban area to be developed, and analyze the influence of the construction of the sewage treatment plant on the current situation of the area and the future water environment, can provide technical support for the rational development and utilization and effective protection of water resources, and maintain the healthy development of economic society. Taking the demonstration of the installation of sewage outlet into the river of Nanjing Longpao New City Sewage Treatment Plant (Phase I) project as an example, COD and NH3-N are selected as evaluation factors, and two-dimensional water quantity and quality model is adopted to predict river water quality, analyze the impact of pollutant discharge on water quality and water ecology of relevant waters, and demonstrate the rationality of the location of sewage outlet.