Abstract: The immiscible poly（ethylene terephthalate）（PET）/polypropylene（PP）blend was prepared by melt mixing and its structural rheology was studied.The results showed that the immiscible morphology influenced both the dynamic and steady-state rheological behavior of PET/PP blend.The blend with dispersed PP domain/PET matrix morphology showed a dynamic shape relaxation，while that with dispersed PET domain/PP matrix morphology only showed a small sensitivity to shear action.For the blend with complicated phase structure，the low-frequency elastic response could be observed clearly.Moreover，the agglomeration of the dispersed drops was the dominant factor affecting the rheological behavior under a higher shear field，while the break-up of drops became the dominant one under a lower shear field.