The work aims to improve the pretreatment efficiency of cellulase and the performance of microfibrillated cellulose (MFC) film. With bleached eucalyptus sulfate pulp as raw material, the activity of cellulase (Cx activity) was regulated by respectively adding cationic polymers polydimethyl diallyl ammonium chloride (PDADMAC) and poly-acrylamide (CPAM). The effects of cationic types and dosage on the tensile strength, oxygen permeability and light transmittance of MFC film were compared and analyzed. PDADMAC with high charge amount and low molecular weight had a greater effect on the improvement of enzyme activity, which improved the pretreatment efficiency of the enzyme. Although CPAM with high molecular weight and high charge amount reduced the enzyme activity, to a certain extent, it effectively controlled the excessive hydrolysis of the enzyme in the amorphous region, which was beneficial to the enhancement of the mechanical properties and barrier properties of the film. The cationic polymers added can improve the Cx activity of cellulase, and thus improve the pretreatment efficiency of cellulase on bleached eucalyptus sulfate pulp, and finally obtain MFC film products with excellent performance.