Ternary composites of Polyamide 6 (PA6), the mixture of Maleated and Unmaleated Ethylene Propylene Diene terpolymer rubber (named EPDM-M), and nanoCalcium Carbonate (nanoCaCO3) were prepared by one-step and two-step compounding routes. The toughness of the composites was tested by impact test. The microstructure morphology of impact surface and etched impact surface was investigated through scanning electron microscope (SEM). The result shows that toughness of the ternary composites with sandbag microstructure was 270 % higher than neat PA6. The SEM morphology shows that strongly elongated microfibrils and deformation are formed in ternary composite with sandbag microstructure, which cause larger shear yielding and crazes in the surrounding matrix to dissipate more impact energy. Additionally, strong ligaments are observed at the crack tip, which could promote plastic deformation and consumption of fracture energy.