The species composition and variation of phytoplankton community were investigated in the Kumho River from October 1990 to August 1991. The total 203 taxa, including Chlorophyceae, Euglenophyceae, Cyanophyceae, Dinophyceae, Chrysophyceae, were indentified. Among them, the dominant species are Chlamydomonas angulosa, Monoraphidium contortum, Pandorina morum, Euglena limnophila, Euglena sp., Scenedesmus acutus, Scenedesmus quadricauda, Scenedesmus spinosus. The standing crops of the phytoplankton community ranged between 290cells/ml at 1 station in March, 1991 and 74280cells/ml at 5 station in June, 1991. Euglenophyceae attained their maximum occurrence during autumn and spring in the downstream. The diversity index and the dominant index were ranged 0.3-1.43 and 0.05-0.99, respectively. According to environmental factors and phytoplankton community, it suggests that the water quality of the Kumho River was ranged from oligotrophic state to mesotrophic state at st. 1 and st. 2, mesotrophic state to eutrophic state at st. 3 and st. 4, hypertrophic state at st. 5.