The properties of polymer alloys and blends strongly depend on their phase structure. Morphological study is thus very important in the design and development of alloys and blends. Computer programs have been developed to predict the dependence of structure and properties on phase separation and shear flow. Phase structures of binary systems were calculated for various blend ratios by solving the phase separation equation using a finite difference method. Thermal conductivity, elastic modulus, and thermal expansion coefficient were predicted from the calculated phase structures by finite element heat, stress, and thermal stress analyses, respectively. The relationships between the structure and properties were numerically investigated. The predicted results for elastic modulus were verified by comparing with experimental data for PC/PS blends.