Abstract: High-voltage direct-current (HVDC) submarine cable is the core device for large-capacity, low-loss, long-distance cross-sea power transmission, which is the key foundation for realizing large-scale offshore wind power grid connection and interconnection of power grids across the sea. Currently, the rapidly growing demands for offshore wind power development require DC submarine cables to have higher operating voltage, larger capacity, and greater length, so higher requirements are put forward for Crosslinked Polyethylene (XLPE) cable insulation materials. This paper firstly reviewed the domestic and international development history of HVDC submarine cables, compared the advantages and shortcomings of XLPE and wrapped insulation. Regarding the scorch problem during the large-length continuous extrusion process and the insulation interface problem of factory molded joints faced by DC submarine cable insulation, the effect and mechanism of the XLPE insulation scorch products and the factory joint insulation interface defects on the space charge and electric field distribution were discussed. The finite element simulation and numerical calculation methods of space charge and electric field distribution characteristics of full-size DC submarine cables were introduced, the evolution of space charge and electric field distribution of DC submarine cable XLPE insulation under steady and transient conditions was analyzed, and the mechanism of the influence of DC submarine cable insulation thickness on space charge and electric field distribution was explained. Finally, the prospects in the future development of DC submarine cable XLPE insulation are put forward, and the key problems that need to be solved for the localization of high-voltage submarine cable insulation are pointed out.