A fungus with high yield of cellulase was screened for enzyme production optimization and enzymatic property exploration to provide a reference for the application of cellulase in regenerated papermaking. Several strains producing cellulase were screened by Congo red identification method, and the CMCase activity of the strains was determined by DNS colorimetric method. The strain with the strongest enzyme production ability and the highest enzyme activity was selected to optimize the enzyme production conditions. Finally, the crude enzyme produced by the strain was collected to explore its enzymatic properties. The results showed that the enzyme production ability of fungus RX-3 was the strongest, and it was identified as Aspergillus sp.. The optimum enzyme production conditions of fungus RX-3 were as follows: wheat bran and peptone were the carbon source and nitrogen source of RX-3, respectively, the inoculation amount was 2%, and the optimum pH environment was 4. The enzymatic properties of cellulase produced by fungus RX-3 were as follows : the optimum reaction time was 25 min, the optimum reaction temperature was 50 ℃, the optimum ratio of substrate to enzyme solution was 3:1, Fe2+ and Mn2+ promoted the enzyme activity, and Zn2+, Mg2+ and Cu2+ inhibited the enzyme activity.