Abstract: PVA/starch/montmorillonite (MMT) nanocomposites were prepared through melt processing. The effect of MMT on the structure and properties of PVA/starch composites was investigated by X-ray diffraction (SAXD), differential scanning calorimeter (DSC), scanning electron microscope (SEM), thermogravimetric analysis (TG), mechanical testing, etc. Starch and PVA molecules destroyed layered structures of MMT during thermal processing. MMT could increase the crystallization temperature, and decrease the crystallinity and melting enthalpy of composites. Significant improvement of tensile strength and Young’s modules were observed due to the fine dispersion of the MMT layers and the strong interaction between MMT and the matrix. The water sorption decreased and water resistant property was improved with the incorporation of MMT, resulting by the restricted swelling of the matrix by MMT nanolayers.