Abstract: In order to study the electrical properties of grafted polypropylene (PP) which can be used as recyclable DC cable insulation and its regulation mechanism, the polypropylene grafted by vinyltriethoxysilane (VTES) was prepared. The breakdown strength, DC resistivity under room and high temperatures, and the related trap characteristics and mechanism were tested and analyzed. The experimental results show that, for the silane-grafted PP, the electrical resistivity is enhanced by 2~3 times at most under the working electric field of the cable insulation layer, and under the two temperature conditions of 30 ℃ and 90 ℃. The breakdown strength can be enhanced by nearly 10% compared with pure PP, and the space charge accumulation is significantly suppressed. Grafted silane can introduce a large number of deep traps into the material. The simulation results show that grafted silane can introduce deep electron trap levels and deep electrostatic potential wells into the material. Traps and potential wells can capture free carriers and affect the charge transport process, thus achieving an increase in resistivity. The work in this paper can provide some references for the subsequent research and development of grafted polypropylene DC cable insulation materials.