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.