The invention discloses a calculation method and system for obtaining the critical environment temperature of the current-carrying capacity of a direct-current cable, and belongs to the technical field of power systems. The method comprises: acquiring direct-current cable insulation material parameters, performing function fitting on the direct-current cable insulation material parameters, and generating a conductivity numerical model; obtaining the equivalent conductivity of the DC cable insulation material, the intermediate point electric field value and the temperature value of the DC cableinsulation material insulation layer and the leakage current of the DC cable insulation material insulation layer according to the conductivity numerical model, and determining the electric field distribution of the DC cable insulation material insulation layer; when it is determined that the electric field in the insulating layer of the insulating material is maximum, the outer-layer temperatureand the maximum temperature gradient of the insulating material of the direct-current cable are obtained; and obtaining an environment temperature relational expression according to the maximum temperature gradient, and calculating the critical environment temperature of the direct current cable by combining a thermal circuit model between the current-carrying capacity and the wire core temperature. Under different environment temperatures, the maximum temperature gradient and the environment temperature critical value of the current-carrying capacity of the cable are controlled through the wire core temperature.