A new approach to produce polypropylene random copolymer/ethylene propylene diene monomer/polyolefin elastomers modified with maleic anhydride/organic modified nanomontmorillonite (PPR/EPDM/POE-g-MA/OMMT) nanocomposites with superior low-temperature toughness was conducted. The brittle-ductile transition temperature (Tbd) of PPR/EPDM/POE-g-MA/OMMT nanocomposites reduced from −20 °C to −40 °C. The incorporation of POE-g-MA results in the distribution of OMMT changing from the interfacial distribution into dispersed inside rubber phase and a compound rubber dispersed phase in PPR/EPDM/POE-g-MA/OMMT nanocomposites was comprised of EPDM, POE-g-MA and embedded OMMT. The synergistic effect of POE-g-MA and OMMT was considered to result from the special compound rubber dispersed phase consisting of EPDM and POE-g-MA as well embedded OMMT, which led to the reduction in space between rubber domains and the increase in internal friction and ultimately brought about the remarkable enhancement in mechanical properties.