Changes of the concentrations of COD Mn, BOD₅and NH₃-N from main sections of the middle and upper reaches of EastRiver were identified, by using the method of seasonal Kendall test for water quality data from Longchuan, Heyuan and Boluomonitoring stations during 2001-2007. The results suggest that: (1) the concentrations of BOD₅ increase significantly at all stations;(2) the concentrations of COD_Mnand NH₃-N do not display a significant trend at Longchuan control section, and the concentrationsof COD_Mn showed a decreasing trend and NH₅-N showed an increasing trend at both Heyuan and Boluo control sections; (3) changein the rate of water quality from the middle reaches is larger than that from the upper reaches; (4) the water quality change is mainlyinfluenced by the change of waste discharge.