Abstract: A novel kind of organic montmorillonite (MMT Ⅱ) , modified with the combination of dodecyl benzyldimethyl ammonium chloride (DBDA) and meta-Xylylenediamine (MXDA) , was prepared by a newly designed modification method , and finely exfoliated MMT Ⅱ/ epoxy nanocomposites were achieved by the aid of shearing force of ballmilling. Fourier transform infrared spectroscopy (FTIR) , X-ray diffraction (XRD) and transmission electron microscopy( TEM) were used to characterize the structure of MMTⅡ and the corresponding nanocomposites. The mechanical properties were tested. The results show that large agglomerates of MMT Ⅱ can not be homogeneously dispersed by generalstirring , which only induces an intercalated or partially exfoliated structure of MMT Ⅱin epoxy matrix at most . Whereasthe exfoliation of the retained intercalation structure or agglomerates can be promoted by external shearing force of ballmilling, which induces homogeneously dispersed nano-sheets of MMT Ⅱ and enhances mechanical properties. Impactstrength can be increased up from 3211 kJ / m² to 4811 kJ / m² , which is about 50 % higher than that of pristine matrix ,and the flexural strength can also be enhanced by about 8 % higher.