Abstract: To improve the insulation properties of polypropylene（PP） blended elastomer composites, the effects of antioxidant-grafted PP on PP blended polyolefin elastomer（POE） are investigated. The physicochemical properties, mechanical properties, and volume conductivity of the graft-modified materials are tested before and after thermal aging. Based on the measurement of short-term breakdown performance, long-term voltage withstand characteristics experiments are conducted, and the residual life of the materials is obtained through fitting analysis. The experimental results show that the grafting modification with hindered phenol functional groups can mitigate the damage of thermal aging to PP/POE composite insulation materials, maintain the original physicochemical and mechanical properties, reduce conductivity, and extend the service life of the materials. Based on quantum chemical calculations, the electrostatic potential and band structure of graft-modified polypropylene chains are obtained. The results reveal that grafting introduces deep potential wells capable of capturing high-energy electrons, thereby enhancing the insulation performance of the material.