A two-step process has been developed to disperse sodium montmorillonite(Na + -MMT) in organic liquid N,N-dimethylformamide(DMF) and was applied in preparation of poly(ε-caprolactone)(PCL) nanocomposites. The dispersion of Na + -MMT particles in DMF was evaluated by laser diffraction and the dispersion of Na + -MMT particles in composites was investigated by transmission electron microscopy(TEM) and X-ray diffraction(XRD). TEM result indicated that the average lateral dimension of Na + -MMT particles in composites was approximately 300 nm and the thickness was less than 20 nm. The impact of Na + -MMT on the crystallization behavior and thermal resistance of PCL were determined by differential scanning calorimetry(DSC) and thermal gravimetric analysis(TGA), respectively. The impact of Na + -MMT on biodegradability of PCL was also studied.