Cellulase plays an important role in the biorefinery process，so it is necessary to deeply understand the mechanism of enzymatic hydrolysis． Cellulose as polymer compound formed by the polymerization of D-glucose， which is an important component of biomass，and the degradation of cellulose is the most significant step in the de- structing process of lignocellulose． Due to its stable molecular structure，only through synergistic action of various domains and components of the cellulase can it be biodegraded into available saccharides． The recent research on the mechanism of cellulase degradation at home and abroad was reviewed． This review firstly explored the interac- tion between structure and function to reveal the relationship of between them and analyzed the molecular mecha- nism of biocatalyst，which provides theoretical basis for optimizing cellulase structure to improve catalytic ability． Secondly，the characteristics and molecular structure of cellulase degradation mechanism were discussed，and the important effect of its enzymatic synergy and environment on the enzyme activity was also investigated in order to provide references for the optimization design of enzymatic hydrolysis system． Finally，by combining the mecha- nism of cellulase biodegradation，the effective ways to reduce enzyme costs was summarized．