Abstract: In order to fit strategic deployment of new energy system driven by the national “dual-carbon” goal, satisfy requirements of long-distance and large-capacity power transmission, and optimize efficiency and reliability of energy transmission, taking the 220 kV main submarine photoelectric composite cable (hereinafter referred to as submarine cable) used in a domestic project as an example, structural design and performance analysis were carried out, as well as capacity enhancement structure design of copper wire-steel wire for armored layer. At the same time, current carrying capacity of landing section under ordinary structure and enhanced capacity structure were calculated respectively, and advantages of enhanced capacity structure were obtained. Subsequently, mechanical properties of submarine cables during laying and salvage were calculated and checked to verify stability and excellence of properties for large-section and large-length high voltage submarine cables with enhanced capacity structure. Results showed that submarine cables with enhanced capacity structure could effectively solve the dual problems of economy and reliability in construction of offshore wind power transmission channel under complex seabed terrain and high corrosion conditions, and support the large-scale development process of far-reaching sea wind power.