System and method for producing cellulosic ethanol through saccharification and fermentation of biomass

The invention relates to a system for producing cellulosic ethanol by saccharification and fermentation of biomass. The system comprises a reactor A for an enzymolysis reaction of a biomass raw material, a reactor B for a fermentation reaction of the biomass raw material, a storage tank for storing the material discharged from the reactor B, and a collection tank for collecting cellulosic ethanol generated by the fermentation reaction of the biomass raw material. The reactor A respectively communicates with the reactor B, the storage tank and the collection tank. The reactor B communicates with the storage tank. The invention also discloses a method for preparing cellulosic ethanol by using the system. The biomass raw material is separately subjected to multiple times of cyclic processes of enzymolysis saccharification, fermentation and ethanol extraction at intervals, such that inhibition of ethanol accumulation on enzymolysis and fermentation processes is effectively reduced, a conversion rate of cellulosic