In order to solve the issue of localised electric field concentration in high‐voltage direct current cable accessories, a method for preparing a composite material with high conductivity and nonlinear conductivity properties is proposed. The authors employed homemade calcium copper titanate @ zinc oxide (CCTO@ZnO) as a filler and glycidyl methacrylate (GMA) as a grafted small molecule to co‐regulate the non‐linear conductivity of silicone rubber (SiR). The results indicate that doping CCTO@ZnO can enable SiR to acquire non‐linear conduction properties and grafting GMA can significantly enhance the conductivity of SiR. However, both doping CCTO@ZnO and grafting GMA have a negative impact on the breakdown performance of SiR. Simulation results indicate that reinforced insulators made from doped and grafted co‐modified composites can improve the distribution of electric fields in cable accessories.