Reclaimed water from sewage treatment plant is an important water resource. Being discharged into the river channel, it can not only alleviate the water shortage, but also maintain the water cycle of the river ecosystem. Although reclaimed water usually meets water quality standards, its nutrients, trace pollutants and organic compounds may still pose potential risks to the channel environment and ecosystems. This paper summarizes the effects of reclaimed water replenishment on river water quality and ecosystem: reclaimed water replenishment helps to improve the river flow, improving river water quality and diluting pollutant concentrations; nutrients in reclaimed water can promote the growth of aquatic plants and algae, improve the self-purification capacity of the river channel, but it may also lead to eutrophication problems; higher temperatures in reclaimed water may negatively impact aquatic species' survival and reproduction, while excess nutrients can cause overgrowth in riparian vegetation, reducing biodiversity and ecosystem balance; reclaimed water provides essential nutrients for riparian vegetation and wetlands, promoting plant growth and ecosystem stability. Although reclaimed water has broad application prospects, in order to ensure ecological security, it is necessary to strengthen water quality monitoring and risk assessment before discharge to achieve sustainable utilization.