Abstract: Isotactic polypropylene grafted with maleic anhydride (PP-g-MAH) and PP-g-MAH filled with Nd₂O₃ or CeO₂ (REOs) were prepared by means of reactive extrusion.The crystallization behavior and crystal structure of PP,PP-g-MAH and PP-g-MAH filled with REOs were studied by DSC,PLM and WAXD techniques.The results show that the crystallization rate of the grafted polypropylene is higher than that of blank polypropylene.Furthermore,the addition of the REO can accelerate the crystallization rate of the grafted polypropylene.After introducing the REO into PP-g-MAH,the heterogeneous nucleation dominates the process of crystallization,and the low active energy for crystallization increases the crystallization rate.In particular,PP-g-MAH filled with CeO₂ has the lowest active energy and the highest crystallization rate.The addition of REOs does not influence notably the nucleation mechanism and growth mode of the crystallization of i-PP,whereas it enhances the equilibrium melting point and equilibrium melting enthalpy of PP-g-MAH.The WAXD analysis indicates that the addition of the REO can increase the crystallite size of the α-form crystal.