The poly(vinylchloride) (PVC) nanocomposite was prepared by melt mixed of PVC with polyhedral oligomeric silsesquioxanes containing vinyl group (V-POSS). The rheological behavior of V-POSS/PVC nanocomposites was investigated by torque rheometer and capillary rheometer. The influences of composition of blends, shear rate, shear stress on melt apparent viscosity and non-Newtonian index (n) were discussed. The dynamic mechanical properties, mechanical properties and morphology were determined. The result shows that the plastic time of nanocomposites decreases while melt viscosity increases with increasing V-POSS content. V-POSS has a good compatibility with PVC. The nanocomposites have better impact strength with increasing V-POSS content. V-POSS can use as process aid and impact aid at appropriate contents.