Abstract: This paper investigates the relationship among the species composition, density of dominant species and community structure of periphytons, and water quality at eight transects along Suzhou Creek in different seasons. The results showed that the species number of periphyton was the greatest in summer and the density of dominant species was the highest in summer and autumn, and the water quality was generally consistent with the tendency of the changes both in the indices of diversity and evenness. There were significant negative correlations between the contents of N and P in water, and the indices of diversity, evenness, algae density, total biomass, while CODcr and BOD5 did not show any significant relationship with these four biological indices. According to above results, the pollution level was relatively low at the transects of Zhaotun and Huangdu, while relatively high at the tansects of Wuning Road and Beixinjing. With regard to the community structure, the dominant species at the upstream were mainly autotrophic algae while those at the middle and downstream were mainly heterotrophic animals, which indicates that the changes in the community structure could reflect the changes in water quality.