Abstract: The surface of calcium carbonate (CaCO₃) was firstly pretreated with maleic anhydride (MAH) to introduce active double bond groups,then grafted chemically by polypropylene wax (PPW) via in-situ solid phase grafting to increase its compatibility with polypropylene. Three kinds of modified CaCO₃ with different chemical grafting ratio of PPW were prepared by changing experimental conditions,and their PP-based composites were produced. The effects of interfacial interaction between CaCO₃-MAH-PPW and PP matrix on the strength of PP-based composite filled with modified CaCO₃ were studied. The results show that the dispersibility of CaCO₃-MAH-PPW in PP is improved,suggesting an improved compatibility between them. With the improvement of grafting ratio of PPW on the surface of CaCO₃,the interfacial interaction between CaCO₃ and PP increases gradually. When the grafting ratio of PPW is 4.48 mg PPW/g CaCO₃,the interfacial interaction between CaCO₃ and PP is strongest and the decrease of tensile strength of composites is the least,the young's modulus increases most at the same time. When m(PP):m(CaCO₃)=100:50,the young's modulus reaches 0.86 GPa,which is the 1.63 times of PP's. When the grafting ratio of PPW is 2.49 mg PPW/g CaCO₃,the interfacial interaction between CaCO₃ and PP is suitable and the notch impact strength of composites improves the most. And when m(PP):m(CaCO₃)=100:10,its notch impact strength is 3.91 kJ/m²,which is the 1.35 times of PP's