The method of doping long-chain branched polypropylene (LCBPP) was employed to enhance the electrical and mechanical capabilities of PP/POE blend polyme applied to cable insulation. The test results revealed that the ternary synergistic blending of PP/POE with LCBPP enhanced the compatibility between polypropylene (PP) and polyolefin elastomer (POE). Under the testing temperatures of 30 ℃ and 90 ℃, the electrical conductivity of the PP/POE cable insulation material doped with 5 wt% LCBPP was lower than that of the PP/POE cable insulation material doped with 0 wt% LCBPP, the breakdown strength was enhanced, and the tensile properties were also enhanced. At 30 ℃ and 90 ℃, 5 wt% LCBPP doped cable insulation material can reduce the leakage conductivity to 30.39%–46.24%, and increase the breakdown strength by 23.68%–33.98%. The findings could give some reference for the performance modification of PP/POE cable insulation.