Polypropylene (PP) is one of the most consumed materials in the world and one of the most environmentally friendly materials. In the past five years, the domestic PP production capacity has increased with an average annual growth rate of 12.4%, which has led to a serious structural surplus of domestic PP, that is, a serious surplus of general products and high-end products rely on imports. Therefore, technological innovation is needed to achieve high performance of polypropylene, and it is necessary to expand the application field to achieve the transition from overcapacity to short supply. Using PP random copolymer (M26ET) as raw material, maleic anhydride (MAH) was grafted onto the PP molecular chain without initiator and solvent through microwave high temperature solid phase grafting technology, so as to realize the polar modification of PP random copolymer, and a new kind of salt-grafted PP random copolymer resin was prepared through alkaline washing. The successful grafting of maleic anhydride was confirmed by FTIR characterization and melt flow index measurement, and the specific grafting ratio was determined using acid-base titration. It was found that long chain branched polypropylene molecules were formed during grafting, and the melt strength was improved via measurement of the rheological performance. DSC and XRD analysis showed that the grafting of maleic acid (MA) and sodium maleate (NaMA) groups was beneficial to the crystallization of polypropylene and the β crystal with toughening effect was produced. The prepared polar resin was used as compatibilizer in PP/polyolefin elastomer (POE)/talcum powder (TALC) composite system. It was found that sodium maleate grafted PP (PP-g-NaMA) with relatively higher grafting ratio could simultaneously improve the rigidity, toughness and heat resistance of the composite materials, and the enhanced effect was better than commercial polar resin, even though its grafting ratio was more than twice.