Abstract: Poly（lactic acid）/ montmorillonite (PLA/MMT) nano-composites were prepared through melt intercalation in a twin-screw extruder. The microstructure, morphology, thermal properties, and crystallization behavior of the nano-composites were characterized using XRD, TEM, and DSC. It revealed that the layer spacing of MMT increased from 1.801 to 3.530 nm by the intercalating of PLA. When 3 % of MMT was used, the tensile strength, elongation at break, and impact strength reached the max. With MMT loaded, the degree of crystallinity of PLA increased and the average grain size reduced compared with neat PLA.