Abstract: Na-montmorillonite was organically modified by the cationic exchange method using 2, 4, 6-tris-(dimethylaminomethyl) phenol (DMP-30) as the modifier. The influence of the molar ratio of DMP-30 to HCl was stu-died on the organic treatment of Na-montmorillonite. The morphologies and structures of the as-obtained samples were characterized by SEM, TEM, IR and XRD. The results show that at a proper molar ratio (1 ∶ 2) of DMP-30 to HCl, the DMP-30 molecules are successfully intercalated into the layers of montmorillonite, and the space of organically modified montmorillonite layers increases from 1.34nm to 1.81nm. Nanocomposites were prepared by the in situ polymerization of epoxy resins in the presence of the organo-modified montmorillonite (OMMT). The structure of the nanocomposites was studied by XRD. The d₀₀₁ peak of the organic montmorillonite disappeared, indicating that the organo-modified montmorillonite was completely exfoliated in the epoxy matrix.