Abstract: A constructed wetland is an effective treatment process for a lightly contaminated river. In order to quantify the main nitrogen removal mechanism and nitrogen transfer processes in a constructed wetland, an eco-dynamic model including various bio-reactions, physical adsorption and sedimentation was established to simulate the nitrogen removal process in Dengbeiqiao constructed wetland. The simulation results showed that the calibrated model could generally address the concentration variations for organic nitrogen, NH₄⁺-N and NO₃^--N. The model efficiencies of simulating organic nitrogen, NH₄⁺-N and NO₃^--N, were 81.2%, 67.6% and 50.2%. The simulation for the nitrogen transfer showed that the major nitrogen removal mechanisms in the constructed wetland were nitrification, denitrification and plant uptake. The denitrification and plant uptake could remove 50.0% and 11.0% of the total nitrogen, respectively. In addition, sediment adsorption accounted for 3.5% of the total nitrogen removal. The average reaction rates of nitrification, denitrification and plant uptake were 0.234,0.438 and 0.050 g/(m³·d) respectively.