Abstract: In order to further enhance safety and stability of cross linked polyethylene insulated polyvinyl chloride sheathed copper core cables, structure and material of cables were optimized by taking YJV-0.6/1 kV 4×120 mm² as an example. Insulation materials and sheath materials before and after optimization were verified by thermal extension, thermal contraction, sheath weight loss, high temperature pressure, low temperature tension. Results showed that insulation thermal extension, insulation thermal shrinkage, sheath weightlessness and low-temperature tensile and other test parameters results of cable insulation materials after optimisation were better than those before improvement, in which elongation under load was reduced from 64% to 40%, permanent elongation after cooling was reduced from 6% to 0, shrinkage was reduced from 2% to 1%, sheath weight loss was reduced from 0.67 mg·cm⁻² to 0.45 mg·cm⁻², indentation depth was reduced from 34% to 22.5%, and elongation at break increased from 135% to 180%, which indicated that safety and stability of cables were significantly improved.