PP-g-MA/layered silicate nanocomposites were prepared by melt intercalation method using PP modified with maleic anhydride (PP-g-MA) by solid-phase grafting process and montmorillonite modified with octadecyl ammonium ion (C18M). The graft level of PP-g-MA was about 2.0% when measured by ¹H NMR and elemental analysis. XRD patterns and TEM micrographs showed that PP-g-MA was successfully intercalated into C18M. A PP-g-MA/layered silicate nanocomposite had higher tensile strength and modulus than PP and PP-g-MA. Especially, it showed a dramatically increased tensile modulus up to the silicate content of 3wt% and the constant modulus over silicate content of 5wt%. Dynamic storage modulus and complex viscosity of the nanocomosites were higher than those of PP-g-MA. They increased considerably up to silicate content of 1 wt%, but increase slowly over this content like the tensile modulus. It was found that the nanocomposites showed the faster crystallization than PP-g-MA.