Abstract: The ultimate aim of bioremediation on the water is to renew the structural and functional characteristic of aquatic ecosystem. In the process of bioremediation, by analysis of the phytoplankton community in the eutrophic water body with bioremediation, the thesis discuss the effect of bioremediation on phytoplankton and the responses of phytoplankton to the changes of environmental facts, in a hope to reflect the effect of bioremediation in accordance with the response of phytoplankton, so as to provide biological proof for illustrating the efficiency of measures taken for the bioremediation. Here follows some components of this test water: water area(350m 2), water dept (60cm), water volume(210m 3).Before testing, Spot survey on water showed it took on a condition of hypereutrophic. Comprehensive measures concerning zoology are taken including the way of adding Bioenergizer, biologic algaecide, effective microbe into water, and planting Macrophyte. The experiment began from 29th.April, 2002. Beforehand, background was sampled once on 27th of April. And after the engineering project, sampling work was done on 16th, and 30th of May, 13th and 27th of June, 7th of July respectively. As the result of the engineering process, there was a great decline on the density and biomass of phytoplankton. Meantime, the species diversity and Shannon-Weaver index have ascended obviously, and species composition and indicator of dominant species changed from mesosaprobic to oligosaprobic. Also the dominant degree changed from extremely high degree to a lower average degree. In addition, the water-bloom of Dictyosphaerium pulchellum were controlled after the engineering brought into operation. The species number of phytoplankton correlated close negatively with PO 4-P but positively with TN/TP. The contents of PO 4-P and the ratio of N/P have big influence to the community of phytoplankton in the water body.