In this study, the morphology evolution, crystallization behaviour, oriented analysis and mechanical performance of micropart and macropart were investigated in detail. Compared with conventional injection moulding, during the filling of melt into the mould cavity, MIM own the higher shear rate and quickly cooling rate. There are the significant differences in the morphology distribution between micropart and macropart due to the significant sample dimension discrepancy. For macropart, the dispersion of PET phase and the interfacial combination are poor and no orientation occurs. For micropart, however, the dispersed phase merges to form continuous and well-defined PET microfibrils along the flow direction in both skin layer and core layer (especially in PPET10 micropart). There are also the significant differences in the crystallization behavior between micropart and macropart. It is observed for the first time that the combined effects of a strong shear flow field and PET microfibrils facilitate the formation of bundle-like β-crystal epiphytic on the surface of PET microfibrils under microinjection moulding. When Tmould is 80 oC, the degree of orientation of the micropart increases and the crystalline structures are highly compact. However, the DSC and WAXD results also show that evaluating the PET content can increase the content of β-crystal and the orientation degree in micropart. In addition, it is also found that relative to macropart, micropart has the increase the formation of β-crystals and lamellar branching capability. The remarkably enhanced shear force field generated under microinjection