Nanoparticles are widely exploited to control the morphology and final properties of immiscible polymer blends. In this work, mechanisms on how NPs distributed at or near the interface affect the morphology and rheology of PP/PS blends is systematically investigated under quiescent annealing, shear flow and extension flow. Distributions of NPs in dispersed phase but near the interface, in the matrix but near the interface and mostly at the interface are constructed by the addition of three kinds of NPs with different hydrophobic properties. It is suggested that, under quiescent annealing, the refinement and stability of the morphology are highly promoted by NPs distributed near the interface of PP/PS blends. Under shear flow, the stabilization of the morphology are significantly enhanced by a small amount of the NPs near the interface while it is unstable with the addition of high concentration of NPs. Under extension flow, the deformation of the dispersed phase are significantly promoted by a small amount of the NPs near the interface, and obvious extensional thinning behavior is observed at high concentration of NPs.