Abstract: Nanocrystalline cellulose (NCC) was oxidized by sodium periodate and further modified by a cationic reagent in distilled water.And then the suspension of cationic nanocrystalline cellulose (CDAC) was directly mixed with chitosan (CTS) dissolved in acetic acid solution.The composite films CTS-CDAC were fabricated by means of solvent evaporation.The structure and properies of NCC before and after modification were characterized by Fourier Transform Infrared spectroscopy (FT-TR),Transmission Electron Microscope (TEM),X-Ray Diffractometer (XRD),Zeta potential and particle size analyzer.The intermiscibility of the suspension of CDAC and CTS dissolved in acetic acid solution effect of the mass fraction of the CDAC in CTS-CDAC composite films on the mechanical properties and water swelling of the CTS-CDAC composite films were studied.As a result,the suspension of CDAC can be mixed with CTS solution well,and CDAC can be uniformly distributed in the CTS matrix.Compared with pure CTS film,the mechanical properties of CTS-CDAC composite film is significantly improved.When the mass fraction of CDAC in the composite film is 12%,the tensile strength reach the highest.In addition,the swelling degree of CTS-CDAC composite film is significantly lower than that of pure CTS film,and the stability of the composite film is better than that of the pure CTS film.