In recent years polymer alloys or polymer blends have become one of the most widely used material in engineering application. To improve the reliability of the materials, extensive studies are required on their fracture behaviors under general loading conditions. Polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) blends were selected in this research to examine the fracture behavior of po9lymer alloys. PC/ABS is the polymer alloy of PC and ABS and its characteristics varies with volume fractions of two components. In this study, fracture test under mode I and mixed mode loading was conducted and fracture behaviors were observed. At a certain value of mixed mode loading ratio with high mode II components, crack due to shear type fracture initiates at the initial crack tip. Fracture toughness and the appearance of shear type fracture depends on blending ratio of PC and ABS. It is suggested that these tendencies related to morphology of PC/ABS blends. Fracture resistance increase under mixed more loading with lower in mode II component, while it reduces with the appearance of shear type fracture.