In order to analyze the scale and water supplement route of a new water purification station in the northern area of Nanjing Qinhuai District, a one-dimensional water quality model of river network was established by coupling HD and AD modules in MIKE11. Ammonia nitrogen and suspended solids were selected as the research objects and the variation of water quality under different water supplement scales and water supplement routes was simulated. The result shows that the scale of 180 000 t/d for the new water purification station and connection of the outlet pipe to the sub branch of the Qinhuai River is appropriate.