According to the annual variations (May 1990-April 1991) of species composition, standing crop and productions of phytoplankton in Houhu Lake, Wuhan, it is found that the dominant taxa are no other than Chloropgyta, Bacillatiophyta and Cyanophyta in the lake with their standing crop and production being highest in autumn and lowest in spring.On the basis of the ecology of phytoplankton community, some comprehensive evaluation on the trophic state of Houhu Lake is suggested.