The dynamic changes in line length of high-voltage transmission lines under different loads can affect the results of traveling wave distance measurement based on fixed line length. This paper assumes that overhead ground wires are not affected by loads. Using ground wires as a reference, image recognition positioning technology is applied to calibrate the relative coordinates of ground wires and transmission lines. Based on the theoretical derivation of overhead line equations, dynamic correction of transmission line length is achieved. Considering the scenarios of equal and unequal heights of transmission towers, based on the catenary equation, the ratio of stress to specific load is transformed into a single variable, and a transmission line length correction model is constructed corresponding to the ground wire transmission line height difference H identified and located by image recognition. It further considers the visual distribution of equidistant multi-point height differences, applies curve fitting technology, and achieves dynamic correction of transmission line length. Finally, the corrected line length is applied to single end and dual end traveling wave ranging, and a comprehensive traveling wave ranging weight allocation based on minimum error is proposed. The simulation verifies the effectiveness of line length correction and ranging accuracy proposed.