Abstract:Referring to the indices of red tide hazard evaluation, cyanobacteria bloom area and Chla concentration was took as evaluation indices and a hazard degree evaluation method was established based on the analysis of cyanobacteria bloom hazard in Taihu Lake. AHP method was applied to determine the weights and fuzzy comprehensive evaluation method was adopted to quantitatively estimate the hazard degree. Cyanobacteria bloom hazards in Taihu Lake in 2008 were evaluated through the above method. The hazards of Taihu Lake in 2008 were mainly small, medium and large, and there were no significant and serious cyanobacteria bloom. In the different hazards, the small hazard distributed each month, and the medium and large hazards were mainly distributed in May and from July to December. The evaluation method could be successfully applied in the scientific research and field operation.