A new compatibilizer with polypropylene as matrix, Glyceryl monostearate (GMS) and styrene(St) as functional group was prepared, and its effect on the properties of polypropylene(PP)/montmorillonite(MMT) nanocomposites was investigated. Fourier transform infrared spectroscopy results showed that the GMS and St monomers had successfully been grafted on the backbone of PP. The characterization results of X-ray diffraction(XRD) pointed out the crystallite size perpendicular to the crystal plane in PP/ compatibilizer / MMT nanocomposites was smaller than that of PP. Through detecting of transmission electron microscope(TEM), it can be found that the new compatibilizer will improve the dispersibility of MMT in PP matrix. At last, the mechanic properties of PP/MMT nanocomposite materials get determination, the mechanical strength especially impact strength had a obvious progress when O-MMT was added, and its maximal value impact strength appears in the 3% montmorillonite and 20% compatibilizer.