To evaluate the relationship between plankton community composition and environmental factors in a city section of the Ba River, the samples were collected and analyzed every two months from September 2016 to July 2017. In the study, 7 phyla and 63 genera of phytoplankton were identified, with the most abundant species of Chlorophyta (34.9%), followed by Bacillariophyta (30.2%). A total of 45 zooplankton species from 4 classes were identified, dominated by Rotifera (48.9%) and Protozoa (24.4%). The abundances of phytoplankton and zooplankton were 0.73×10⁴ to 98.5×10⁴ ind/L and 20 to 1084 ind/L, respectively. The spatial and temporal distribution of abundances of both phytoplankton and zooplankton showed a decreasing trends from the downstream to the upstream, with the peaks in summer. The water quality was comprehensively evaluated using plankton abundance, Shannon diversity index, Margalef abundance index, and physicochemical indexes including transparency, dissolved oxygen, total phosphorus, total nitrogen, permanganate index, and heavy metal content. The results showed that the city section of the Ba River was moderately polluted and that the aquatic plants in the river bed of the upstream landscape river have the ability to remove the pollutants. Canonical correspondence analysis indicated that water temperature, total nitrogen, pH, dissolved oxygen,and mercury are the key factors in phytoplankton community distribution, and that water temperature, total nitrogen, total phosphorus, chlorophyll-a, and mercury are the key factors in zooplankton community distribution.