Lignin is one of the important components of lignocellulosic cell walls, which endows plant cell walls with rigidity and strength and protects them from microbial invasion. The presence of lignin is thought to hinder the conversion of biomass to bioenergy, so understanding enzyme-lignin interactions is very important in order to reduce the inhibition of lignin and improve the hydrolysis yields. Conversion of lignocellulosic raw materials into bioethanol is divided into pretreatment, enzymatic hydrolysis, and fermentation. In this paper, both pretreatment and enzymatic hydrolysis of lignocellulose are described in detail. Finally, the reasons why lignin hinders enzymatic hydrolysis efficiency, mainly from forming spatial barriers and interacting with cellulase, are discussed, and the influencing factors and mechanisms of action of cellulase hydrolysis are explored with a view to targeted regulation of lignin structure to improve lignocellulosic saccharification.