One-step reaction compatibilized microfibrillar reinforced iPP/PET blends(CMRB) were successfully prepared through a “slit extrusion-hot stretching-quenching” process.Crystallization behavior and morphology of CMRB were systematically investigated.Scanning electronic microscopy(SEM) observations showed blurry interface of compatibilized common blend(CCB).The crystallization behavior of neat iPP,CCB,microfibrillar reinforced iPP/PET blend(MRB) and CMRB was investigated by differential scanning calorimetry(DSC) and polarized optical microscopy(POM).The increase of crystallization temperature and crystallization rate during nonisothermal crystallization process indicated both PET particles and microfibrils could serve as nucleating agents and PET microfibrils exhibited higher heterogeneous nucleation ability,which were also vividly revealed by results of POM.Compared with MRB sample,CMRB sample has lower crystallization temperature due to existence of PET microfibrils with smaller aspect ratio and wider distribution.In addition, since in situ compatibilizer tends to stay in the interphase,it could also hinder the diffusion of iPP molecules to the surface of PET phase,leading to decrease of crystallization rate.Two-dimensional wide-angle X-ray diffraction(2D-WAXD) was preformed to characterize the crystalline structure of the samples by injection molding,and it was found that well-developed PET microfibrils contained in MRB sample promoted formation ofβ-phase of iPP. One-step reaction compatibilized microfibrillar reinforced iPP / PET blends (CMRB) were successfully prepared through a “slit extrusion-hot stretching-quenching” process. Crystallization behavior and morphology of CMRB were systematically investigated. Scanning electronic microscopy (SEM) The crystallization behavior of neat iPP, CCB, microfibrillar reinforced iPP / PET blend (MRB) and CMRB was investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM) crystallization temperature and crystallization rate during nonisothermal crystallization process indicated both PET particles and microfibrils could serve as nucleating agents and PET microfibrils exposed higher heterogeneous nucleation ability, which were also vividly revealed by results of POM. Compared with MRB sample, CMRB sample with lower crystallization temperature due to existence of PET microfibrils with smaller aspec t ratio and wider distribution.In addition, since in situ compatibilizerbly to stay in the interphase, it could also hinder the diffusion of iPP molecules to the surface of PET phase, leading to decrease of crystallization rate. Two-dimensional wide-angle X -ray diffraction (2D-WAXD) was preformed to characterize the crystalline structure of the samples by injection molding, and it was found that well-developed PET microfibrils contained in MRB sample promoted formation of β-phase of iPP.