Abstract - The distributions of phytoplankton community are investigated from 29 reservoirs in Yeongsan and Seomjin River Basins, Korea. As a microalgal flora, a total of 424 species of phytoplankton were identified. They were 157 Chlorophyceae, 161 Bacillariophyceae, 39 Cyanophyceae, and 67 other algal taxa. The phytoplankton diversity were low in stream type reservoirs such as Kumho, Youngsan and Youngam Reservoirs. The population density of phytoplankton ranged from 29 cells mL-1 to 53,161 cells mL-1. The dominant phytoplankton species more than 20% of total standing crops were Asterionella formosa, Aulacoseira ambigua, Aulacoseira distans, Aulacoseira granulata, Cyclotella sp., Synedra acus, Coelastrum reticulatum, Pandorina morum, Scenedesmus arcuatus, Aphanothece clathrata, Microcystis aeruginosa, Phormidium sp. The concentration of chlorophyll a ranged from 0.41 mg m-3~220.72 mg m-3, and showed highest concentration in Gaecho-je. The concentrations of TN and TP have no clear relationships with chlorophyll a concentrations.