Simulating the thermal-mechanical state of overhead conductors under wildfire conditions is of great value for evaluating the probability of wildfire-induced faults in transmission corridors and assessing power grid operational risks. To meet the simulation requirements for the thermal-mechanical state of overhead conductors in wildfire environments, a thermal-mechanical state simulation method for overhead conductors under wildfire conditions is proposed. First, the influence mechanism of wildfires on the thermal-mechanical state of overhead conductors is analyzed. Then, the thermal radiation and convective heat transfer from flames and smoke are incorporated into the conductor thermal balance model. On this basis, the mechanical equations of the conductors are coupled to construct and solve a comprehensive mathematical model that describes the combined effects of wildfire, current loading, and environmental conditions on the thermo-mechanical state of overhead conductors. This allows the simulation of conductor temperature, stress, and sag within a given time period during wildfire spreading. Finally, case studies verify the effectiveness of the proposed method and analyze the impact of line current loading on the conductor’s thermal-mechanical state under wildfire conditions. The results provide technical support for estimating ground discharge probability, assessing power grid operational risks, and developing safety control strategies for transmission lines exposed to wildfires.