To analyze the dynamic characteristics of changes in water environment capacity, this paper takes the Shiwuli River, one of key waters in Hefei, as the research object. Moreover, aiming at the main pollutant index ammonia nitrogen and total phosphorus, the hydro-water quality coupling model, based on the MIKE11 water quality model HD module and AD module, is constructed to calculate the water environment of the river capacity. In the meantime, it is compared with the traditional one-dimensional model calculation method. The results showed that the water environment capacity of the Shiwuli River based on the MIKE11 water quality model shows obvious dynamic characteristics. The monthly average water environmental capacity of ammonia nitrogen and total phosphorus in the Jinzhai Road section are -2.83 g·s^-1 and -5.86 g·s^-1 respectively, while what is in the bridge section is -15.64 g·s^-1 and -1.07 g·s^-1 respectively. It has higher calculation accuracy than the one-dimensional model. All in all, this method not only provides the basis of widely using MIKE11 model, but offers a new way to calculate the dynamic water environment capacity of the Shiwuli River. Most importantly, a new idea for the calculation of dynamic water environment capacity can be adopted by other similar polluted rivers.