Sodium carboxymethylcellulose/montmorillonite nanocomposites were prepared by using the solution intercalation technique．The (001) diffraction peak was not observed in the X-ray diffraction partem of the composites．TEM studies indicated that the silicates were exfoliated and distributed in the carboxymethyIcellulose matrix at the nanometer level．Infrared spectroscopy analysis revealed that the interaction between the ether oxygen atoms of the celulose molecules and the silicon-oxygen and/or the aluminum-oxygen bonds of montmorillonite might be the driving force for intercalation for the composite system The thermal stability and the tensile strength of the sodium carboxymethylcellucose nanocomposites were improved and their water vapor permeability was decreased as compared to those of the pure polymer.