Abstract: Based on the water quality data of 8 sections in the Three Gorges Reservoir from 2003 to 2017, the statistical analysis and seasonal Kendall method were used to analyze the status, water period characteristics and interannual variation trend of the reservoir water quality. The results showed that:(1) current water quality of the main stream section in the Three Gorges Reservoir was mainly in class Ⅱ～Ⅲ and tended to be better along the course, the water quality of Linjiangmen section on tributary Jialing River and Wulong section on Wujiang River were mainly in class Ⅳ to inferior Ⅴ and the main over-standard project was total phosphorus; the permanganate index and total phosphorus concentration were characterized by high water period > flat and dry water period, and ammonia nitrogen concentration was characterized by flat, dry water period > high water period.(2) The proportion of over-standard reservoir water and the concentration of permanganate index, ammonia nitrogen and total phosphorus were decreasing. In addition, the decrease amplitude of permanganate index and ammonia nitrogen were greatly in the reservoir storage period, while the decreasing amplitude shrank in the reservoir operation period, which was consistent with the interannual trend of COD and ammonia nitrogen emissions in industrial wastewater. The decrease amplitude of total phosphorus was small in the reservoir water storage period, and the amplitude increased in the reservoir operation period, which was closely related to the use of chemical fertilizer and pesticide.