PC/PLA composite material introduces the degradability of PLA to PC with great performance, but their compatibility and impact resistance are poor. Aiming at this deficiency, ABS is used to modify PC/PLA. This paper established the ternary compound system of PC/PLA/ABS by melt blending and studied the impact of adding ABS and compatibilizer ABS-g-MAH on the composite’s morphology, thermal properties, rheology and mechanical properties. The results showed that: ABS bettered the brittle fracture of PC/PLA and improved the impact strength of composite with the optimum proportion of 30% of PC/PLA mass. In addition, ABS-g-MAH effectively improved the compatibility of the composites as well as mechanical properties of materials. With the increase of ABS, the crystallization ability of PLA in the composite improved and the thermal stability of the system deteriorated slightly, the melt shear viscosity of composite also decreased.