Abstract: To investigate the migration and transformation, spatial distribution, phytoremediation process, and coupled response mechanisms of nitrogen and polycyclic aromatic hydrocarbons (PAHs) in reclaimed water wetlands, an urban wetland in Beijing that is completely recharged by reclaimed water was selected as a representative case study. The water area was divided into a phytoremediation area, a semi-phytoremediation area, and a non-phytoremediation area. A systematic analysis was conducted on the levels, spatial distribution, and phytoremediation efficiency of nitrogen and PAHs in the water and sediment. In-situ comparisons were made to elucidate the response mechanisms at different levels of phytoremediation. The results showed that: (1) ∑PAHs contents in the water column and sediment ranged from 10.6 to 326.3 ng/L and 29.4 to 1245.9 ng/g, respectively. The average contents of total nitrogen were 6.09 mg/L and 1250.4 mg/kg, respectively. (2) Phytoremediation proved to be an effective means of nitrogen removal from the water column, notably decreasing the average total nitrogen (TN_w) concentration from 8.87 mg/L upstream to 3.44 mg/L downstream. Furthermore, phytoremediation was more effective in removing middle-ring PAHs from water and low-ring PAHs from sediment. (3) Phytoremediation altered the coupled response mechanisms between nitrogen and PAHs content. In the water column, the concentrations of nitrogen and PAHs in phytoremediation area exhibited a synergistic effect, while an antagonistic effect appeared in non-phytoremediation area due to the interception of sediment. (4) In the sediment, the non-phytoremediation zones displayed a positive correlation between nitrogen and PAHs content due to their shared source. However, aquatic plants caused the correlation between them to disappear. The research showed that reclaimed water inputs nitrogen and PAHs pollution into receiving wetlands. The hydrophytes can synergistically degrade these two types of water pollutants, and promote each other through the mediation of denitrifying bacteria, resulting in a positive feedback mechanism. This study not only enhances the understanding of the evolution of nitrogen and PAHs in reclaimed water wetlands, but also provides valuable reference for the protection of the water environment in similar wetlands.