Abstract: The properties of XLPE insulation material directly affects the operation safety of power cables. The existing research on XLPE is mostly based on experiments, and the research property is relatively single, lacking comprehensive properties analysis based on numerical calculation. In the paper, a molecular model for analyzing the dielectric, mechanical, thermal and water-resistance properties of XLPE is established and simulated. The influence of crosslinking degree on the properties of XLPE is studied, and the corresponding influence mechanism is obtained. By comparing with the experimental data, the results of molecular simulation is verified. The results show that the improvement of crosslinking is conducive to the improvement of mechanical and thermal properties of XLPE. Among them, at room temperature, the increase of elastic modulus is up to 480.4%, and the increase of thermal conductivity is up to 16.78%; moreover, the glass transition temperature increases by 53.9 K. Under the synergistic effect of electricity and heat, the influence of crosslinking degree on the water resistance of XLPE and the relative dielectric constant of water containing molecule XLPE is not linear. Then, the comprehensive properties of XLPE under different crosslinking degrees are evaluated by combining analytic hierarchy process and weighted method, and the crosslinking degree for improving the comprehensive properties of XLPE is obtained. The conclusion can provide reference for the production of XLPE for cable insulation.