Abstract: This paper reports the investigation on phytoplankton community of Huangpu River with 5 sampling sites during Apr.2004 to Feb.2005,with counting the cell number and identifying the species composition of phytoplankton flora,and determination of some physical and chemical index of water quality.The water quality was evaluated with biological indication,Shannon-Wiener and Margalef diversity index.The results illustrate that the water body of Huangpu River is in class V in summer and in class IV according to the National Standard(No.GB3838-2002),Huangpu River is in β-mesosaprobic stage assessed by the analysis of succession of dominant species,species composition of phytoplankton,the Shannon-Wiener’s index and Margalef index.The indicators of β-mesosaprobic stage are the diatom of Melosira granulata and its varieties,and the green algae of Scenedesmus quadricauda,etc.