A combination of polymer blending and nanoscale filler reinforcement has proved to be an efficient strategy to develop a new family of polymer nanocomposites with a great tailoring potential for producing products with a variety of prescribed properties. Changes in the material properties of the nanocomposite are strongly linked to the interaction of polymer segments and the particle surface and how this interaction influences the state of particle dispersion. Optimization of nanocomposite properties requires deeper understanding of how variation of polymer segment-surface interaction affects the state of the particle dispersion. Rheology is a powerful tool for gaining an integrated picture of the nanocomposites materials since it can provide information for mastering the process parameters that lead to controlled microstructure, which in turn enables control of the end-use properties. Thus the relationship between the structure and rheology of polymer nanocomposite is of practical interest for two reasons: firstly, rheological properties are very sensitive to changes of microstructures for heterogeneous polymers, and they are simpler to use than analytical methods, such as nuclear magnetic resonance. Secondly, it is the rheological properties that govern the flow behaviour of polymers when they are processed in the molten state. Therefore, the linear and nonlinear viscoelastic behavior of nanocomposites have received considerable attention from both academia and industries. In this presentation we demonstrate how the rheology can be utilized to provide more insight into understanding parameters affecting microstructure, of nanoparticle filled polymer blends, with emphasize on flow induced nanoparticle orientation and restructuring along with nanoparticle localization and its influence on polymer blend morphology. In this context the relationship between results of the linear and nonlinear viscoelastic experiments will be discussed.