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Based on water quality surveys over 2 years (July to December,in 2014 and 2015) in a typical arid river in northem China the Xingtai segment of the Fuyang River basin-the variation of nitrogen (N) and phosphorus (P) was analyzed.The extent of water eutrophication of this segment was also assessed using a universal index formula for eutrophic evaluation and a logarithmic power function.The results showed that the average concentration of total N (TN) was 27.2 mg/L (NH3-N,63.5％),total P (TP) was 2.0 mg/L (solution reactive phosphorus,68.8％).Temporal and spatial variations of N and P in this segment were observed.Concentrations of N and P in the arid season were higher than those in the rainy season.Spatially,the N and P concentrations followed the same trend;i.e.,higher in the city segment than in the suburbs,and decreasing along the river.The water eutrophication in the studied segment reached extremely high levels at all times (eutrophication index ≥76.3).Spatially,its trend was clearly linked with N and P.Water shortage,pollution accumulation and a weak self-purification function are the main reasons for the prominent eutrophication in this segment.