Abstract: Wastewater treatment plant effluent is a reliable source of ecological flow for urban river and lake systems due to its stable quantity and controllable quality. In order to improve the environmental safety of replenishing water and explore its influence on the receiving water bodies, Wangjiangou River in Hefei City was taken as the research object. In this study, the water quality was monitored along the replenishing river during the dry and wet periods, and the spatial and temporal distribution characteristics of nitrogen and phosphorus forms and dissolved organic matter (DOM) in the receiving river were analyzed. The results showed that: (1) The water quality of Wangjiangou River was improved, and the concentration of pollutants increased along the river. The water quality index in the wet period was higher than that in the dry period, and total nitrogen (TN) was the main influencing factor. (2) The main form of nitrogen in the replenishing water was dissolved inorganic nitrogen (DIN, 60.9%), of which nitrate was the main form. Except for dissolved organic nitrogen (DON) and nitrite (NO₂⁻-N), the concentrations of other forms were higher in the wet period than those in the dry period. (3) Phosphorus was mainly in dissolved inorganic form (DIP, 80.3%), and the concentrations of all forms of phosphorus were higher in the wet period than in the dry period. The concentrations of nitrogen and phosphorus increased along the replenishing river. (4) In both dry and wet periods, DOM was predominated by humic acid-like substances, accounting for more than 68%, with strong autogenous and low humification characteristics. The average relative molecular weight and content of DOM were higher in the wet period than in the dry period. These results suggests that the effluent of the wastewater treatment plant will result in increase in nitrogen and phosphorus loads of the replenishing river, which will play positive roles in enriching the river′s hydrodynamics, ensuring ecological flow and ecological restoration of urban rivers. Simultaneously, we should take into account of reducing the loads of non-point source pollution that flow into the receiving river during the wet period.