A way to improve high-temperature mechanical behavior and reduce conductivity of direct-current cable insulation material is introduced by using low-crosslinked linear low density polyethylene (LLDPE). LLDPE and low density polyethylene (LDPE) with different dicumyl peroxide (DCP) content are analyzed. The mechanical properties of LLDPE and LDPE with DCP are assessed by hot-set test,dynamic mechanical analysis (DMA) and tensile test. The DC conductivity and DC breakdown strength of these materials are also tested. The results show that crosslinked LLDPE behaves better than LDPE does in elongation in the range from 0.7 wt.% to 2.0 wt.% DCP addition,and corssslinked LLDPF meets the requirements of HVDC cable insulation for crosslinked polyethylene (XLPE) elongation with 0.7 wt.% DCP addition. In this condition,LLDPE with 0.7 wt.% DCP addition is chosen to be a substitute for traditional XLPE for the purpose of minimizing by-products. DMA and tensile test results verify that LLDPE with 0.7 wt.% DCP addition has higher Young's modulus and elongation at break than traditional XLPE does. DC conductivity and DC breakdown experiments show that LLDPE with 0.7 wt.% DCP addition has low conductivity,good temperature stability of conductivity and DC breakdown strength at the temperature range from 30 ℃ to 90 ℃. As the crosslinking by-products in the actual cable are difficult to be removed completely and unevenly distributed, it seriously affects the long-term safe operation of the cable. The low crosslinked LLDPE is recommended as the replacement of the traditional XLPE for the insulation material in HVDC cable insulation system,so as to reduce DC conductivity and enhance the temperature stability of conductivity while meeting high temperature mechanical properties.