The property of starch film improved by montmorillonite was studied.The result showed that;the water resistance of the films was improved effectively and the retrogradation of the films was delayed by adding montmorillonite .With the addition of montmorillonite increased,the tensile strength and water dissolution time gradually increased, while the elongation gradually decreased.The optical microscopy analysis of the film surface suggested that; the films surface became more flat and smooth by adding montmorillonite.The addition of montmorillonite was better less than 3%,otherwise the membrane became more brittle and the mobility of the thermoplastic starch was lower.