Abstract: The new energy transmission corridor in Xizang will inevitably pass through extremely cold land areas, and the grounding device is facing the risk of freezing failure. In previous studies, the premise of calculating the dispersion performance of the grounding device is to consider the frozen soil as a static horizontal layered structure, ignoring the influence of the overall heat dissipation effect on the soil freezing structure when the grounding device is connected to the tower, thus resulting in the inaccurate analysis of the dispersion performance of the grounding device in actual operation. Therefore, the coupling model of soil water and heat field considering the heat transfer of the grounding conductor is established in this paper, and the soil structure under different freezing times is calculated. Then the failure model for scattered flow of grounding device is constructed. Finally, compared with the traditional model, the influence of the radius and length of the grounding conductor and the initial soil temperature on the dispersion performance of the grounding device is explored. The results show that due to the good thermal conductivity of the grounding conductor, the soil it contacts is easy to form local freezing, and compared with the traditional model, the failure time of the same grounding device at a low temperature of −10℃ is about 18 days earlier. If the low temperature duration is the same, a single vertical conductor with a radius of 6 mm will not fail when it reaches 3.3 m, which is a difference of about two times compared to 1.6 m under the conventional model. In addition, reducing the radius of the grounded conductor or decreasing the thermal conductivity of the grounded conductor can slow down local freezing.