Montmorillonite (MMT), a kind of reinforced additive and glycerol-plasticized thermoplastic starch (GTPS) were used in the preparation of Montmorillonite-reinforced themorplastic starch composites(MTPSC) with the method of melt extrusion. Scanning electron microscope (SEM) revealed that MMT were uniformly dispersed in GTPS. Fourier Transform infrared (FT-IR) patterns showed that in the MTPSC the C-O groups of starch molecules shifted to the higher wavenumber, while the reactive hydroxyl groups of MMT shifted to the lower wavenumber. That was caused by the cooperation of the strong absorption that existed between MMT and starch molecules and hydrogen bonds that formed between the reactive hydroxyl groups of MMT and the hydroxyl groups of starch molecules. MMT was on the submicron filling transition state and acted as an obstructor. When MTPSC was stored for 14 days at RH (relative humidity) = 39%, the tensile strength, Young's modulus and breaking energy of MTPSC were 27.34, 206.74 MPa and 1.723 N m, respectively. It was obvious that the mechanical properties of MTPSC were greatly improved. At the same time, the effect of water content on the mechanical properties was studied. X-ray diffraction revealed that MMT restrained the crystallization of GTPS effectively. Differential thermal analysis (DTA) and water absorption testing showed that the thermal stability and water-resistant properties of MTPSC were better than those of GTPS. (C) 2004 Elsevier Ltd. All rights reserved.