Abstract: Environmental factors cause overheating sections to appear along the route of high-voltage cable laying, thereby limiting the load current of the entire cable. To address the impact of these overheating sections, taking 640kV cross-linked polyethylene DC cable as the research object, a method using a water circulation cooling system to increase the cable"s carrying capacity was proposed. A "electric-thermal-flow" multi-physics field coupled finite element model was established to analyze the changes in temperature and carrying capacity in each layer with and without the water cooling system; the data obtained from the finite element simulation were used for response surface design to analyze the influence of single parameters and multi-parameter interactions of the water cooling system on the increase of the cable"s carrying capacity. The research results show that the adoption of a water cooling system can effectively reduce the temperature of the cables and increase their carrying capacity; it was found that with the increase of arrangement density and water flow temperature, the cable carrying capacity also increases nonlinearly, but it tends to stabilize at a certain value; with the increase of water flow temperature, the cable carrying capacity decreases linearly; it was revealed that the arrangement density has the most significant impact on the cable carrying capacity, and the combined effect of arrangement density and water flow temperature thickness can achieve the maximum increase in the cable carrying capacity.