The invention provides a method and system for obtaining temperature rise of a high-tension overhead transmission line. On the basis of a heat balance equation, a product of a skin effect coefficient and an iron loss coefficient is used to calculate the AC/DC resistance ratio. The AC/DC resistance ratio is a nonlinear function of current-carrying capacity and temperature, the equation to be solved is complex, but a result is more accurate. A Newton iterative method is used to solve the equation, the steps for calculating the current-carrying capacity and temperature are provided, and the relation of the AC/DC resistance ratio and the current-carrying capacity in different environmental conditions is calculated. Via calculation, the temperature rise value of the high-tension overhead transmission line is calculated.