Abstract: Combined with the life cycle assessment method and analytic hierarchy process method,the environmental impact assessment was carried out on the fermentation process of three typical cellulosic biomass,namely poplar wood,corn straw and bagasse,to produce fuel ethanol. Six environmental types,namely acidification,eutrophication,global warming,fossil energy consumption,photochemical pollution and human toxicity,were analyzed and compared. Three different perspectives were selected to analyze the environmental impact of biomass fermentation process. The results show that the greenhouse effect of agricultural stage and production stage is the highest in the whole life cycle process. In the global perspective,the impact of global warming is relatively high,and in the regional and local perspective,the acidification of the process is the most serious.