Abstract: As a promising thermoplastic insulating material for HVDC cables, polypropylene (PP) is expected to replace the conventional cross-linked polyethylene (XLPE) insulation. The PP-based modification technology for HVDC cable insulation includes copolymerization/blending, nanocomposites, and grafting modification. To make a comprehensive evaluation of the modification technical routes above, copolymerized PP, PP-based nanocomposites, and grafting- modified PP were chosen and prepared, respectively. The thermal, mechanical, and DC dielectric properties were tested and compared with XLPE. The results indicated that compared with conventional XLPE, the PP-based modified materials showed superior thermo-stability and similar mechanical properties. Whereas the dielectric properties under DC condition were significantly enhanced. Among them grafting- modified PP performed the best. PP-based grafting modification is of excellent comprehensive performances and applicable in large-scale industrial production, therefore showing excellent application potential and development value.