Abstract: This study aims to investigate the water quality variations of Boshang Reservoir. Based on monitoring data from January 2020 to October 2023, a single-factor evaluation method was employed to analyze the changes in water quality. The research focused on the variation patterns of Chemical Oxygen Demand（COD）, five-day Biochemical Oxygen Demand（BOD₅）, Permanganate Index(COD_Mn), and pH. Integrating the climatic background and surrounding environmental factors of Linxiang District, the causes of water pollution were explored. The results indicate that the reservoir's water quality is co-influenced by multiple factors, including climate, domestic sewage, and agricultural activities. Key contributors to the periodic deterioration of water quality include the low collection and treatment rate of domestic sewage, nutrient release from sediment（endogenous pollution）, and agricultural non-point source pollution. Accordingly, this study proposes several targeted recommendations: strengthening the control of agricultural non-point source pollution, rationally planning centralized livestock and poultry farming areas, shifting to organic agriculture to reduce the use of chemical fertilizers and pesticides, and implementing reservoir dredging.