Aeeording to the analysis of the cyanobacteria bloom disaster effect, this paper discussed the evaluation indices and criteria of the hazard, constructed hazard evaluation method applying fuzzy comprehensive evaluation model.In the indicator layer, the affected population was the population affected by the hazard.The affected area included the percentage of the cyanobacteria bloom area and affected days.The eco-environmental indices included cyanobacteria cell concentration,total nitrogen concentration and total phosphorus concentration.The economic losses included direct loss and indirect loss, and it took the drinking water loss and tourism loss as direct losses and the hazard relief loss as indirect loss.Through the analysis of indicator system.according to the experts' determination, the cyanobacteria bloom hazard classification in Lake Taihu was divided into five classes which were light damage, mid-damage, heavy damage, heavier damage and catastrophic damage.Based on the fuzzy comprehensive evaluation method, this paper evaluated the cyanobaeteria bloom hazard events from 2004 to 2008.The results showed that the cyanobaeteria bloom hazard event in May 29th, 2007 was catastrophic one,which was consistent with the socio-economic effect.The results proved that the evaluation method could be successfully applied in the scientific research and field operation.