The effects of annealing on microstructure and mechanical properties of an impact resistant polypropylene copolymer(IPC) were investigated. Different annealing temperatures ranging from 80 °C to 160 °C were selected. The phase reorganization of IPC during annealing process was studied through morphological characterization technologies, including scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The crystalline structure changes in the IPC sample, including the i PP matrix and PE component, were investigated using wide angle X-ray diffraction(WAXD) and differential scanning calorimetry(DSC). Dynamic mechanical analysis(DMA) was used to analyze the relaxation extent of IPC before and after annealing. The results showed that annealing induced phase reorganization in IPC and the degree of phase reorganization depended on annealing temperature. The annealed IPC samples exhibited largely increased crystallinity compared with the unannealed one. Intensified damping peak with increased molecular chain mobility was achieved for the annealed IPC samples. At an appropriate annealing temperature(140 °C), largely enhanced impact strength was achieved for the annealed IPC sample. The toughening mechanisms were analyzed based on the phase reorganization and relaxation behavior. The effects of annealing on microstructure and mechanical properties of an impact resistant polypropylene copolymer (IPC) were investigated. Different phase temperatures ranging from 80 ° C to 160 ° C were selected. The phase reorganization of IPC during annealing process was studied through morphological characterization technologies , including scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystalline structure changes in the IPC sample, including the i PP matrix and PE component, were investigated using wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) was used to analyze the relaxation extent of IPC before and after annealing. The results showed that annealing induced phase reorganization in IPC and the degree of phase reorganization depended on annealing temperature. The annealed IPC samples exhibits greatly increased crystallinity compared with the unannealed one. Intensified dampi ng toughening mechanisms were harvested for the annealed IPC samples. At an appropriate annealing temperature (140 ° C), largely enhanced impact strength was achieved for the annealed IPC sample. The toughening mechanisms were analyzed based on the phase reorganization and relaxation behavior.