The influence of the distribution of the inorganic particles on the toughness of the PP/EPDM/nano-ternary composites was investigated. Four morphologies for PP/EPDM/nano-ternary composites were obtained by means of adjusting the surface tension of inorganic particles (nano-CaCO3, hydrophobic nano-SiO2 and hydrophilic nano-SiO2) and the compounding sequence (one-step extrusion and two-step extrusion). Morphological observation revealed that the segregated dispersion morphology was formed in the PP/EPDM/CaCO3 composite. For the PP/EPDM/R974 (hydrophobic nano-SiO2) composite, R974 particles were dispersed at the interface between the PP matrix and EPDM dispersed phase. A200 particles (hydrophilic nano-SiO2) continuously dispersed between PP and EPDM phase for PP/EPDM/A200 composites prepared by one-step, while were present in EPDM dispersed phase for the two-step PP/EPDM/A200 composites. The dependence of the toughness on the phase morphology of the components, especially the distribution of nanoparticles, was studied systematically. The impact strength of one-step PP/EPDM/A200 composites was pronouncedly enhanced, increasing 552% compared to pure PP. Compared with the other three composites, the one-step PP/EPDM/A200 composites exhibits better effect of preventing crack propagation and far higher fracture energies. It is attributed to the A200 particles continuously dispersed between EPDM phase and matrix, which makes EPDM particles have better compatibility with the PP matrix and the overlapping of the stress field with A200 particles.