Abstract: Abstract: The effectiveness of enzymatic hydrolysis of cellulose is a key limiting factor for the economical and efficient bioconversion of lignocellulosic materials into fermentable sugars. A group of important factors which could influence the economic and efficiency of the cellulase catalytic reaction was deeply discussed, such as, screening and isolation of strain with a high level of cellulase collected from agricultural field soil or forestry land soil, breeding a hyper cellulase producer after a series of mutation process with a variety of mutation strategies, an engineering singular componet cellulase producing strain constructed by the gene manipulation, factors influencing the cellulase activity in the liquid states fermentation system, the enzymatic hydrolysis mechanism of cellulase especially the important and widely accepted presumption of cellobiohydrolase(CBH) catalytic hydrolysis procedure, the influenza of enzymatic catalytic hydrolysis of lignocellulose after a pretreatment as well as the optimization of the enzymatic hydrolysis mixture. Particularly, both the critical limiting factor of the filter paper cellulase activity in the liquid state fermentation system and the vital limiting single cellulase component in the enzymatic hydrolysis of lignocellulosic materials after a pretreatment were all deeply discussed from a novel perspective. Comparision and analysis the hyper enzymatic activity of CBH, EG(endo-gluconase), BGL(β-glucosidase) as well as FPA(filter paper activity) from a large number of related literatures, it could be presumed that CBH just was the critical enzymatic component which could determine the enzymatic activity of filter paper in the overall fermentation system in the presence of hyper activity of BGL. Furthermore, analyzing the decline rate and the residual activity of CBH、EG、BGL as well as FPA in the enzymatic hydrolysis system, it was assumed that the CBH could also determine the FPA and hence it could be the crucial enzymatic component in the cellulosic materials depolymerizing system. In other words, CBH was not only the critical enzymatic component which plays a crucial part on the enzymatic activity value of FPA but also exerts a critical effect on the enzymatic hydrolysis efficiency in the cellulosic materials after a pretreatment. It is worth mentioning that there is a possibility to demonstrate the spatial distribution of microorganism with a high-level of cellulase in nature. Moreover, it is credible that the FPA value of microorganism isolated from the nature without any mutation ranged from 0.02-5.00 FPIU/mL. In addition, it should be mentioned that the credible FPA value of those hyper producers such as the Trichorderma reesei Rut-30 and the Penicillium decumbens JU-A10 as well as other notable cellulase producing strains isolated from the nature. To be specific, the filter paper activity (57.00 FPIU/mL) maybe the highest value among a great number of reports throughout the world. Finally, it was highly stressed that the revelation of rate-limiting reaction step of enzymatic hydrolysis procedure and the demonstration of the forming mechanism for the critical limiting factors could be the major focus in the field of biomass bioconversion associated with cellulase catalytic hydrolysis. And hence, the foundation of the mechanisms relevant to the vital limiting reaction step will provide a theoretical guidance for the protein engineering improvement of CBH's catalysis efficiency and specific activity.