Abstract: The polyamide 6 (PA6)/polyethylene terephthalate (PET) blends with an encapsulation structure were prepared by means of a twin-screw extruder combined with a high-pressure capillary rheometer, and the effect of viscosity ratio of two components on the encapsulation structure of the blends was investigated under different shear ratesin the extruding process. Polarized light microscopic and scanning electron microscopic observations showed that the PET phase could eventually migrate into the surface of the extrudate to encapsulate the PA6 phase. Raman spectroscopy indicated that the aggregation level of PET phase changed in the radial direction at the interface of two components, which ensured good interfacial properties of final products. In addition, the melt viscosity matching of two components was a necessary precondition for the formation of the encapsulation structure. Moreover, there was an optimal range of shear rate (or viscosity ratio range), and the encapsulation structure obtained in this processing condition is relatively perfect.