Montmorillonite (MMT) modified asphalts are prepared by melt blending with the help of high-speed shear mixer. The dispersion of MMT layers in the asphalt matrix are characterized by X-ray diffraction (XRD). The effect of different contents of MMT on physical properties of the base asphalt is studied. These properties include penetration, softening point and ductility. The results indicate that MMT/asphalt may form a nanocomposite structure with MMT layers intercalated by the asphalt molecules. MMT can improve the high temperature performance and temperature sensitivity of the base asphalt. And it can slightly reduce the low temperature performances of matrix asphalt. It is found that low temperature performances, high temperature performance and temperature sensitivity of the modified system achieved balance when the content of MMT is 4 wt%.