Abstract: Cellulase pretreatment was utilized to treat the poplar alkaline peroxide mechanical pulp (APMP) in present study to improve its papermaking performance and expand the application. The results showed that the beating energy consumption of the pretreated APMP decreased by 19% maximum and water retention value increased by 12.6%, compared to the virgin APMP. Meanwhile, the breaking length, bursting index and tearing index of the papersheets, which were furnished by pretreated APMP and blended with different ratio of softwood bleached kraft pulp (BKP), increased maximum by 6.1%,44.6% and 30.3% respectively. However, the bulk, brightness and the opacity were decreased slightly. The fiber quality analysis(FQA), scanning electron microscope(SEM) and X-ray diffraction(XRD) were employed to characterize. The analysis results indicated that the fiber length increased by 7.0%, the fines content decreased by 10.0%, and the curl index decreased by 22.4% compared with the pretreated APMP with the virgin APMP. Beside, a 0.7% increase of the crystallinity was observed. Cellulose pretreatment can improve the fiber quality of poplar APMP. The resulted in a better physical strength property.