Abstract: The kinetics of isothermal and non isothermal crystallization of Polypropylene (PP) and PP/nanomontmorillonite composites is investigated by differential scanning calorimetry(DSC) and the data have been analyzed with Avrami equation and ZHAO Zhi ying method respectively. It is shown that the montmorillonite nanoparticles can change the isothermal and non isothermal crystallization behavior of PP, enhance the crystallization rate and improve the crystal structure.