Abstract: Based on the monthly monitoring data of 23 water quality indexes of Wulie River basin in 2014, a comprehensive water quality evaluation was performed using single-factor assessment and comprehensive evaluation index method. Utilizing principle component analysis (PCA), the main pollution indicators in the river basin and the regional spatial variation characteristics of the water quality were determined. Furthermore, the pollution sources in the basin were analyzed. According to the results, the water quality of upper tributaries was in Class Ⅱ, the water quality of monitoring sections S1 and S3 in main stream was in Class Ⅲ, and that of monitoring sections S2 and S4 in main stream was in Class Ⅳ. The main pollution indicators were BOD₅ and TP. The PCA results showed that PC1 included COD _Cr and COD_Mn, the PC2 included NH₃-N, DO and BOD_5. There were four main pollution sources including domestic sewage, industrial wastewater, agricultural fertilizer and pesticide inputs, and livestock and poultry raising waste.