The crystallization behavior of partially melting isotactic polypropylene (iPP) has been carefully examined by the differential scanning calorimetry (DSC) and polarized light microscopy. The experimental results show that the unmelted material can accelerate the primary nucleation rate and the ordered structure of polymer melt can speed up the linear growth rate of spherulite, so the crystallization of partially melting iPP proceeds very quickly. The Avrami exponent of partially melting iPP sample is about 2, which indicates that the crystallization mechanism of iPP ordered melt after partial melting is different from that of unperturbed equilibrium melt.