Abstract: Montmorillonite ( MMT) were modified by cetyl trimethyl ammonium bromide ( CTAB) , then, chitosan / montmorillonite ( CS/MMT) composite food preservative films were prepared using chitosan and modified MMT.The tensile properties, thermal performance were measured.The materials were characterized by XRD, FTIR and SEM.The results showed that with the dosage of CTAB increase, the tensile strength of the composite membrane increased gradually.The maximum tensile strength was obtained when the dosage of CTAB /MMT ( w /w) was 0.6.XRD indicated that with the increase of the dosage of modifier the interlayer spacing increased.SEM showed that CTAB could improve the dispersing ability of MMT in CS.After the modification with CTAB, CS/MMT composite formed the layer structure.The tensile properties of the CS/MMT composite films increased significantly.