Field investigations on the phytoplankton community were carried out in December 2005 and June 2006 in shallow lakes of plainriver network areas, Suzhou City. Results show that there are 73 species, 62 genus, 8 phylum phytoplankton, which is mainly composed of the Chlorophyta, Bacillariophyta and Cyanophyta. In winter, the average phytoplankton abundance is 254.88 x 10(4) cells x L(-1), and the Bacillariophyta abundance accounts for 62.3% of the total. While in summer, the average phytoplankton abundance is 2704.28 x 10(4) cells x L(-1), and the Cyanophyta abundance accounts for 93.5%. The relationship between 62 genus of phytoplankton and 11 environmental factors from 57 sampling sites in research area was studied by Canonical Correspondence Analysis. It suggests that water temperature, permanganate indexes, nitrate nitrogen and total nitrogen are the main environmental factors correlated with the distribution of phytoplankton community. And in winter, pH, ammonia nitrogen and total phosphorus are also the main environmental factors. Furthermore, the Bacillariophyta has higher adaptability to the changeable environment. The Chlorophyta can tolerate higher concentration of permanganate indexes, phosphorus nutrients, nitrogen nutrients and total organic carbon, whereas the response of Cyanophyta to environmental factors needs further research.