Abstract: To explore the spatiotemporal variation patterns of surface water quality in Yangzhou and their driving factors, eight water quality indicators from 46 water quality monitoring sections were analyzed in this paper. The surface water quality of Yangzhou from 2021 to 2024 was analyzed using the principal component analysis (PCA) method and the water quality index (WQI) evaluation method. Based on the WQI results and the K-means clustering algorithm, the main driving factors affecting the surface water quality were identified. The results show that: Except for Gaoyou Lake and Shaober Lake where total phosphorus exceeded the standard, all indicators at each monitoring section met the requirements of Class III water quality standards during the research period. The potential water environmental risk indicators in Yangzhou mainly originated from domestic pollution and agricultural pollution. The WQI value ranged from 73.18 to 75.15, indicating that the water quality in Yangzhou was good. The main controlling factors affecting the surface water quality in rural areas were TP and NH₄ -N, and they were BOD₅ and COD_Mn in urban areas. The results can provide a theoretical basis for water environment management and water supply security in Yangzhou.