Abstract: During the period from Sept. 1981 to Aug. 1982, phytoplankton had been collected in Dong Hu(East Lake),Wuhan,Hubei Province. 91 species,varieties and forms of the Chlorophyta, Pyrrophyta arid Cryptophyta had been noted. Among them, 1 species and 1 form are described as new a science; 11 species, 1 variety and 3 forms are recorded for the first time in China.In the species identified, 12 species are frequently encountered in the water of plentiful organic material, or 14% of the total green algae species. In every month of a year, the frequently encountered species appeared repeatedly in the water of plentiful organic material accounted for nearly 50%. The species and quantity of Desmids were very rare. Dominant species were mainly blue-green algae. These characteristics related intimately to entrophication process in Dong Hu.