Danjiangkou Reservoir is the water source area of Mid-route of the South-to-North Water Transfer Project in China,and water quality is one of the critical factors to measure the success.However,the water quality has always been troubled by the water pollution control of input rivers of Danjiangkou Reservoir.This paper analyzed the spatial variations of the water quality in Jianhe River by analyzing regional representative factors such as water quality and man-made interferences based on ecological investigation of the water environment.On the basis of river geographical feature,Jianhe River was divided into four survey sections: upstream, midstream,downstream and Taijihu Reservoir,and the objectives of water environmental management were targeted to level Ⅱ, Ⅲ,Ⅳ and Ⅲ (GB/T 3838-2002),respectively.The results show that under the influence of fertilizing aquaculture,lacking sewage network and a low rate in sewage treatment plant,TN of the whole Jianhe River exceeded threshold fairly and four survey sections all cannot reach the objectives of water environmental management;TP,CODCr,and NH₃-N reached level Ⅱ and Ⅲ,respectively, in upstream and midstream,while only 64%, 64% and 18% in downstream reached level Ⅳ,and only 71%,29% and 0 in Taijihu Reservoir reached level Ⅲ,respectively.The overall pollution patterns are in the form of downstream >Taijihu Reservoir >upstream >midstream,and the major pollutant in Jianhe River was TN (2.27-13.51 mg/L),followed by NH₃-N (0.25-13.31 mg/L),CODCr (7.0-95.5 mg/L) and TP(0.01-0.79 mg/L).Concentrations of CODCr and TP were low and not the main pollutants of Jianhe River.According to the difference analysis of the water quality,the targeted reduction plan was proposed, which provided the scientific basis for better management of water pollution in Danjiangkou Reservoir and water pollution control of the river.