To reveal the community structure characteristics of plankton in the Henan section of the Yellow River,three samplings were conducted at 15 sites in May 2023, October 2023, and February 2024. Qualitative andquantitative analyses of plankton in the samples were carried out. The analysis was conducted from five aspects:the species composition, density, biomass, dominant species, and biodiversity of plankton. A total of 134 species(genera) of phytoplankton belonging to 8 phyla, mainly Chlorophyta and Bacillariophyta, followed by Cyanophyta,were detected at the 15 sites. A total of 66 species (genera) of zooplankton belonging to four major groups weredetected, among which Rotifera had the largest number of species, followed by Protozoa. The abundance ofphytoplankton ranged from 6.02×10⁴ to 11.71×10⁶ cells/L, with an average of 10.92×10⁵ cells/L, and the biomasswas 0.06–5.83 mg/L, with an average of 0.66 mg/L. The abundance of zooplankton ranged from 3 to 2180 ind/L,with an average of 164.03 ind/L, and the biomass was 0.001–3.363 mg/L, with an average of 0.330 mg/L.One-way analysis of variance showed that there was a significant difference in the density of phytoplanktonbetween May and October (P＜0.05), but no significant difference between May and February (P ＞ 0.05). Therewere significant differences in the density of zooplankton between May and October and February (P＜0.05). Therewere significant differences in the biomass of zooplankton and phytoplankton between May and October andbetween May and February (P＜0.05). Chlorella sp., Ankistrodesmus spp., Chlamydomonas spp., Oocystis spp.,Melosira granulata, Synedra acus, Cyclotella spp., and Fragilaria spp. were the dominant species ofphytoplankton in different periods. Brachionus calyciflorus, Asplanchna girodi, Bosmina spp., Diaphanosoma spp.,Daphnia spp., Harpacticoida spp., and Nauplius spp. were the dominant species of zooplankton in differentperiods. The Shannon-Wiener index value of phytoplankton ranged from 0.66 to 4.38, with an average of 2.70. TheMargalef species richness index value was 1.32–4.68, with an average of 2.70. The Pielou species evenness indexvalue was 0.16–0.97, with an average of 0.63. The Shannon-Wiener index value of zooplankton ranged from 0.50to 3.02, with an average of 1.70. The Margalef species richness index value was 0.32–2.33, with an average of1.14. The Pielou species evenness index value was 0.39–1.00, with an average of 0.84. According to thebiodiversity index evaluation criteria, the recent water quality level of the Henan section of the Yellow River wasslightly polluted.