Based on the investigation of water quality of Panxi River in different seasons, 2010, we assessed the diurnal variation of water quality in different seasons and the characteristics of water quality changes within a day by using non-parametric test, analysis of variance and grey relationship analysis. The results showed that the differences were not significant for Zn and Cu (P > 0.05), but significant differences existed among the pH, EC, DO, COD, TP, TSS, BOD5, NO(3-)-N, TN, NH(4+)-N, Pb and Cd contents. It showed that the minimum DO concentration occurred in winter, and the maximum of BOD5, COD and TOC concentrations occurred in winter, and the maximum NO(3-)-N concentration occurred in summer and the minimum TN, NH(4+)-N and TP concentrations occurred in summer. The diurnal variation of dissolved heavy metals showed relatively larger fluctuations in different seasons. The diurnal variation of different water quality parameters presented distinct patterns: diurnal variation of organic pollutants and nutrients showed the peak at 12:00 to 16:00 and dissolved heavy metals peaked at 12:00. The results of grey relationship analysis for surface water indicated that the water quality in spring was in the II class at 06:00 and 08:00 and was inferior to theV class for the rest hours; and the water quality in summer was in the II class; and the water quality in autumn was inferior to the V class at 06:00 and 16:00 and was in the II class for the rest hours; and the water quality in winter was in the II class at 08:00 and was inferior to the V class for the rest hours.