Based on the monitoring data of water quality at 5 stations in Lake Baiyangdian in the past 30 years, this study comprehensively applied multivariate statistical analysis methods and literature research to systematically reveal the trends of water quality evolution, influencing factors, and control measures in Lake Baiyangdian. Results showed that: ①The years 2005 and 2015 were the periods of poor water quality in Lake Baiyangdian over the past 30 years. From 2022 to 2023, the water quality of the lake area remained stable at Class Ⅲ, and by 2023, the water quality was at its best level over 30 years. The main pollution indicators in recent years have been COD and TP. ② From 2009 to 2023, the COD, TN, and TP concentrations in the Dianqu area were in significant downward trends, with an annual decrease rate of 0.611 mg/(L·a) (α=0.05), 0.212 mg/(L·a) (α=0.01), and 0.013 mg/(L·a) (α=0.05), respectively. ③The water quality indicators across various monitoring stations in Lake Baiyangdian could be spatially categorized into three groups, with the Nanliuzhuang station in the western region showing the poorest water quality. Eutrophication indicators were further classified into two categories, with northern sites exhibiting a higher nitrogen-to-phosphorus ratio than the southern sites. Over recent years, Lake Baiyangdian has become predominantly phosphorus-limited despite being a nitrogen-polluted system overall. ④The inflow and water level were the key factors affecting the water quality of Lake Baiyangdian in recent years. From a regional perspective, targeted management strategies were necessary for different areas of the lake. In the western region, particularly at the Nanliuzhuang site, efforts should focus on controlling external nutrient inputs. In the northern sites, priority should be given to reducing total nitrogen concentrations, while in the southern sites, the main focus should be on controlling chemical oxygen demand and total phosphorus levels. In the next step, the multi-site and multi-factor observation data should be further combined with the application of a hydrodynamic-water quality coupling model for simulation and traceability analysis, which can guarantee the comprehensive decision-making of water quality in Lake Baiyangdian, and provide support for the ecological water replenishment and the control of endogenous pollution such as substrate and humus, as well as the synergistic pollution management in the watershed.