In this paper,recent research progress on the mechanism of cellulose degradation by cellulase is studied.The new theory points out that overlooking of cellulose's sup-molecular structure may be the main reason for difficulties in degrading cellulose.The paper briefly describes the research progress on the factors that would influence cellulose degradation by cellulases,such as temperature,pH,time of enzyme reaction and inhibitor,activator.Also,the paper identifies the problems existing in the degradation of cellulose by cellulase and suggests its research direction for the future work.