To obtain a nitrocellulose membrane with enhanced mechanical properties, cellulose nanofibrils(CNFs) with nanometer-diameter and micron-length were obtained by 2,2,6,6-tetramethylpiperidine-1-oxyl(TEMPO) oxidation-sonication treatment of bamboo pulp. The N,N-dimethylformamide(DMF) and DMF/H₂O mixed solvent were used as dispersing agent. And the nitrocellulose was thoroughly mixed with the acidified or unacidified CNFs. CNFs-enhanced nitrocellulose membranes were prepared under different dispersion conditions. In addition, the morphological dimensions of CNFs and the change rule of mechanical properties of CNFs-enhanced nitrocellulose membranes were characterized by transmission electron microscope(TEM), thermogravimetric Analysis(TG), mechanical tensile test and dynamic mechanical thermal analysis(DMTA). Results shows that the diameter and length of CNFs are 5-10 nm and 500-3000 nm, respectively. The acidified and unacidified CNFs have better dispersity in DMF than in acetone. The agglomeration of CNFs occurs when the volume fraction of water in DMF/H₂O reaches 20%. Using DMF as a dispersant, the tensile strength and tensile elongation of the composite membrane prepared by adding acidified CNFs are 52.0 MPa and 10.4% respectively, significantly higher than those of the blank sample (36.6 MPa, 8.4%).