Abstract: In order to better design the structure of high voltage direct current (HVDC) crosslinked polyethylene (XLPE) insulated submarine cable and speed up insulation localization process of DC submarine cable, conductivity of XLPE material from HVDC submarine cable at different temperatures and different electric field intensities were determined by testing method of cable insulation conductivity. Simulation software COMSOL Multiphysics was used to analyze temperature field, electric field intensity and space charge distribution inside the insulation of DC submarine cable under the same laying condition and different load currents by step-by-step coupling analysis method. Simulation results showed that step-by-step coupling analysis method could significantly reduce model solution time and improve computational efficiency. Under the normal working condition, temperature gradients and electric field intensity gradients would be generated inside the insulation of DC submarine cables, which could lead to variations in conductivity and furtherly affect the distribution of electric field intensity in the insulation. When load current inside the cable core increased to a certain extent, field intensity inversion phenomenon appeared. Besides, space charge accumulation occured on both inner and outer surfaces of insulation. Corresponding simulation results could provide reference for the subsequent structural design of DC submarine cable, and provide theoretical basis for the development of domestic raw materials of DC submarine cable.