Abstract: Multi-walled carbon nanotubes(MWCNTs) were modified through grafting C₁₆ alkyl chains. MWCNTs/polypropylene(PP) composites were prepared through solution blending. The crystallization behaviors of MWCNTs/PP composites were studied. The experimental results show that 3% (mass fraction) grafted MWCNTs with C₁₆ alkyl chains could be dispersed very well in PP matrix.The grafted MWCNTs could be dispersed on nano-scale. The presence of the grafted MWCNTs does not change the α-crystal form of PP. The introduction of the grafted MWCNTS induces the heterogeneous nucleation of PP in the grafted MWCNTs/PP composites, which will affect the mechanism of nucleation and the crystal growth of PP. After the addition of 3% (mass fraction) grafted MWCNTs in the PP matrix, the crystallizing temperature is increased by 8℃, the crystallizing rate is improved one time, and the crystallinity of PP matrix is increased by 3%. Moreover, the spherulity size decreases.