Fifteen One-meter-deeped cores were drilled in West Lake, Hangzhou, in 1991.The vertical distribution of microfossil algae in the sediment were analyzed, in order to study the algae succession and trophic developing process of West Lake.Three zones were divided as follows (1) Epiphytic algae zone (Eunotia spp.-Cymbella spp.-Gomphonema spp.assem.):-85cm to-45cm deep, mainly made up of acidobiotic and acidophilous species which were suitable for the bog stage in 2000 years ago.(2) Transitive zone from epiphytic algae to phytoplankan (Aphanizomenon flos-aquae-Melosira spp.assem.): usually existed in a depth between-30cm to-40cm, consisted of indifferent species combining with some alkaliphilous species, indicating that the lake had entered into mesotrophic stage-(3) Phytoplankton zone (Fragilaria construens var.venter-Scenedesmus quadricauda-Lyngbya contorta assem.): At the depth of-30cm and above alkaliphilous species became the dominant species and its density were increased indicating that the lake had been entered into eutrophic stage.Around the depth of-10cm, the density of microfossil algae reached the peak value, representing a hypertrophic stage of West Lake.At the depth of-10cm and above, the density of microfossil algae were decreased, which maybe relative to the government's comprehensive control of eutrophication after 198Q