In this study, the Dongguan River in Taizhou City was selected as a typical river of the Wenhuang Plain, in Zhejiang Province. The MIKE11 water environment mathematical model was established, and then calibrated and validated based on simultaneously monitored data of water quality and quantity. In order to ensure that the water quality in the control section of the Dongguan River would reach the standards, nine schemes for model calculation in the research area were used with comprehensive consideration of hydrologic factors, pollutant reduction, and water transfer. According to the results, in the recent period, as the proportion of pollutant reduction reached 60%, and the amount of water transferred from the Changtan Reservoir reached 20 million cubic meters, the water quality of the Dongguan River reached the grade Ⅳ level. For a long period, as the proportion of pollutant reduction reached 90%, the water quality of the Dongguan River almost reached the grade Ⅲ level, meeting the functional area requirement. This study aims to provide technical support for comprehensive environmental improvement of the Dongguan River.