Abstract: The construction of a new power system with offshore wind plant as the main new power supply is a major strategy to achieve the goal of carbon peak and carbon neutrality. 66 kV flexible cable, as the key equipment, has become the mainstream power collection method for offshore wind turbines above 10 MW, but its working environment and heat dissipation conditions are poor, so it is urgent to improve the ampacity of this type of cable. Therefore, the main insulation and sheath materials with high thermal conductivity are prepared, and the ampacity improvement effect of high thermal conductivity 66 kV wind turbine cable is simulated by finite element simulation, and the temperature distribution of high thermal conductivity cable under different loads is calculated by analytical method. It is found that the modified materials have better electrical insulation performance than the raw materials, and the thermal conductivity of insulating materials and sheath materials are increased by 90% and 52% respectively, and the ampacity of 66 kV wind turbine cable is increased from 682 A to 720.2 A. Under the same load current, the maximum temperature of high thermal conductivity cable decreases by 8.4 ℃. The research results provide an effective method for improving the ampacity of high-voltage wind turbine cables, and provide relevant reference for the simulation calculation of high-voltage three-core cables.