Abstract: In order to understand the growth of phytoplankton in city rivers in Suzhou City, and to provide scientific basis for the improvement of water environment, the water condition and the species composition of phytoplankton were investigated in Miaojia River in Suzhou City from May to December in 2004. Results showed that there were 73 species of phytoplankton belonging to 6 phya, in which scenedesmus and diatom were predominant. Through analyzing Chla., biomass and population of phytoplankton,the density of phytoplanktons ranged from high to low in the following season order: summer＞autumn＞spring＞winter. This result indicated primarily the water's polluted character and the growth of phytoplankton in network of waterways in city, and it provided important references for water quality improvement and restoration.

Key words: phytoplankton, city river, lagging water body, growth rule