Rheology is the science that deals with the way materials deform when forces are applied to them. There are two principal aspects of rheology. One involves the development of quantitative relationships between deformation and force for a material of interest. Another aspect the development of relationships that show how rheological behavior is influenced by the structure and composition of the material and the temperature and pressure. This concept of rheology is very useful and powerful tool in development of industrial materials, so it has wide application to R&D area of industrial company. In this work, it holds two examples which are applied in industrial material development. One is the investigation of the effect of dissolved supercritical carbon dioxide on the viscosity and morphological properties for PE/PS blends in a twin screw extruder, the other is the fabrication of PVDF hollow fiber membrane and elucidation of the membrane morphology as functions of dope and external coagulant rheology in the phase inversion process.