The thermal aging phenomenon that is common in power cables during operation is likely to accelerate insulation failure, limit the service life of equipment, and even cause power system failure. Nanoparticle doping modification can improve the thermal stability of polyethylene matrix materials, and related research can provide solutions for improving cable insulation life. LDPE/TiO₂ nanocomposites are studied, and the effects of nanoparticle concentration, aging time and aging temperature on the dielectric properties of the materials are studied under heat aging conditions. The experimental results show that the doping of TiO₂ nanoparticles can improve the dielectric properties of LDPE matrix materials. When the filling fraction of TiO₂ nanoparticles is 0.5%, the dielectric properties of nanocomposites are the best. The aging time and aging temperature affect the dielectric properties of materials. Two important factors of characteristic deterioration, as the aging time increases and the aging temperature increases, the dielectric properties of nanocomposites deteriorate more. Nano-modification of polyethylene materials while reducing the operating temperature of the cable is of great significance for improving cable insulation life.