Dispersion of clay in polymer matrices is important to improve their engineering performances. Here we report the effect of solvent on dispersion of montmorillonite (MMT) in an epoxy matrix by examining transmission electron micrographs and X-ray diffraction of MMT/epoxy composites prepared with solvents with different polarities. We found that N-metyl-2-pyrrolidone (NMP) used as a polar solvent exhibited the improved dispersion of MMT in the epoxy owing to positive interaction energies with components, which prevents the aggregation of MMT platelets. The solvent-assisted dispersion of MMT significantly increased the corrosion resistance of MMT/epoxy nanocomposites pre-coated onto steel plates.