Abstract: The nano-CaCO₃ / PP composites modified by four kinds of compatibilizers were prepared respectively.The crystallization and melting behavior of PP - base composites were investigated using DSC and WXRD. Theresult s indicate that the addition of nano-CaCO₃ increases the crystallization temperature of PP and induces the formation ofβ-PP crystal due to the heterogeneous nucleation of nano-CaCO₃ . The heterogeneous nucleation of PP-g-AAand PP-g-MA is also observed for PP crystallization. The synergism of heterogeneous nucleation of nano-CaCO₃and PP-g-AA ( PP-g-MA or POE-g-MA) further increases the crystallization and melting temperatures of nano-CaCO₃ / PP composites. Addition of PP-g-MA and POE-g-MA induces the formation of moreβ2PP crystal in nano-CaCO₃ / PP composites. However , addition of EVA-g-MA decreases the heterogeneous nucleation of nano-CaCO₃ .The result s suggest that the heterogeneous nucleation of PP in nano-CaCO₃ / PP composites depends on the interfacial interaction between nano-CaCO₃ and PP , which is influenced by compatibilizers.