[Objective] The temporal and spatial distributions of water quality in a typical basin of rare earth mining areas in the Upper Ganjiang River were analyzed to reveal the change and causes of water pollution and provide a theoretical basis and data support for water environment governance.[Methods] Three methods-descriptive statistical analysis, water pollution index, and correlation analysis-were used to analyze the six water quality indicators of 10 monitoring sections in the Taojiang River basin from 2014 to 2017.[Results] ① The pollution status of each monitoring section of the Taojiang River basin in various hydrological periods was different, and the temporal and spatial differences in ammonia nitrogen content were the most obvious. ② The evaluation results of the water pollution index showed that the water qualities of type Ⅱ and type Ⅲ accounted for 55% and 29%, respectively. The Longtou beach section was dominated by type Ⅴ water, with the worst water quality.[Conclusion] Analysis of the causes of water pollution revealed that ammonia nitrogen was the most dominant pollutant in Taojiang River basin. Rainfall had a significant impact on the water environment in that basin. Moreover, industrial activities, dominated by rare earth mining, as well as various agricultural activities, were important factors causing water environmental pollution.