Objective The water environment factors and plankton compositions of six monitoring sections at 3 hydropower stations along the upstream, midstream and downstream of the Qiuxiang River were investigated, and the water ecological status of the Qiuxiang River was clarified.

Method The comprehensive nutritional status index, biodiversity index and redundancy analysis were used to analyze the water quality status, the community structure characteristics of plankton and the relationship between them, respectively.

Result The water transparency, concentrations of Chla, total phosphorus, total nitrogen and permanganate were 0.32-0.53 m, 0.10-0.43 mg/L, 0.6-5.3 mg/L, 1.39-4.33 mg/L and 0.70- 3.90 mg/L, respectively. The water quality status of the Qiuxiang River was at medium nutrition level according to the comprehensive nutritional state index. A total of 53 species of phytoplankton and 62 species of zooplankton were identified.The abundance of the phytoplankton was ranged from 5.1×10⁸ to 1.89×10⁹ cells/L and that of the zooplankton was ranged from 3.93 to 232.87 ind/L. Chlorophyta, Bacillariophyta, Cyanophyta, Protozoa and Rotaria were the dominant species among phytoplankton and zooplankton. Based on the comprehensive plankton diversity index, the pollution of Qiuxiang River was at the medium level.

Conclusion The upper reaches of the Qiuxiang River has been polluted to a certain extent, and the degree of pollution along the river is reduced. Dissolved oxygen is a key environmental factor affecting the structure of the plankton community in the Qiuxiang River.