Studies on community structures of phytoplankon, including genus richness, density and biodiversities, and regressionanalysis between community index of phytoplankon and water quality parameters were carried out from Jan. to Dec. of 2007 in XixiWetland of the first project-circled aera, Hangzhou. 56 genus of algae were found, of which 73.21% were Chlorophyta andBacillariophyta. The annual mean density of algae from Ⅰ station to Ⅳ station were 2.88×10⁸, 0.37×10⁸, 0.47×10⁸and 0.71×10⁸cells/Lrespectively, of which 93.76% were Chlorophyta and Cryptophyta, and the Chlorella, Cryptomonas and Chamydomonas weredominated in the algae community. The algae diversity indexes of Genus Marglef from Ⅰ station to Ⅳ station were 1.17, 1.10, 1.08and 1.06 respectively. According to values of algae comprehensive index, Xixi Wetland has suffered serious pollution and can beregarded as eutrophication status. Logarithm density of algae was positively correlated with COD Mn value in station Ⅰ and station Ⅲ(P<0.01), and positively correlated with water conductivity value from Ⅰ station to Ⅳ station(P<0.01).