The community composition and density of the phytoplankton and environmental factors of 7 rivers in 7 destricts of Shanghai in August of 2011 were intestigated . In order to provide scientific basis to control the pollution , principal components analysis (PCA) and canonical correspondence analysis (CCA) were applied to analyze the relationships between the phytoplankton community structure and water parameters and to assess the environmental status of the water quality in the suburbs. 189 species of 8 phyla were identified ,including Chlorophyta (74 species), Bacillariophyta (45 species), Cyanophyta (41 species), Euglenophyta (18 species), Xanthophyceae (4 species ), Cryptophyta (3 species), Pyrroptata (3 species) and Chrysophyta(1 species). The dominent species were Chlorophyta, Cyanophyta and Bacillariophyta. PCA analysis showed that DO, water nitrogen, phosphorus and COD_Mn were the main chemical factors affecting the phytoplankton abundance in the water bodies. CCA analysis indicated that SS, water nitrogen, phosphorus, COD_Mn and pH were the main factors driving the phytoplankton abundance and community structure. Results from combining biomass and dominance with diversity index of phytoplankon community structure showed that Liyaojing River in Qingpu and Qianzhong River in Fengxian district were in mesotrophic to eutrophic state,Xiejinggang River in Jinshan district was in mesotrophic, others were in mesotrophic to eutrophic state. Phytoplankton such as Dactylococcopsis rhaphidioides, Cryptomonas erosa and Cyclotella menighiniana etc were defined as the pollution indicator species of rivers in suburb in summer.