By investigating Tuohe River section in Suzhou City,this study used the Dongguanzha station as the sampling point to analyze the main index of water quality based on the continuous monitoring data of Tuohe River from 2004 to 2009.The monitored water quality indicators are DO,BOD,COD,NH₃-N,TN and TP.Based on the method of single factor evaluation,the intuitive graphical interpretation,the linear trend analysis and seasonal Kendall test were used to explore the seasonal and interannual trends of water pollution of Tuohe River.The results indicated that:(1)Water quality changed significantly during a year,the content of DO NH₃-N and TP were higher in winter,while TN and COD were higher in spring and autumn,and the BOD content was higher in summer.(2)The inter-annual variations of BOD,NH₃-N and TN showed significantly downtrend,while there was no obvious change about COD.In general,water quality of Tuohe River section in Suzhou City is becoming better.