Conductive concrete has a good application prospect in transmission line tower grounding. The electrothermal effect and thermal stress distribution under lightning current impulse have an important influence on the design, application and maintenance of conductive concrete foundations. Based on the principle of thermoelectric coupling, the lightning current impulse model of conductive concrete foundation under electric-thermal-mechanical coupling is established by using COMSOL Multiphysics. The electric potential distribution, heat distribution and thermal stress distribution of the conductive concrete foundation are simulated and analyzed, and compared with conventional transmission line tower foundation. The simulation results show the conductive concrete foundation, as a natural grounding body, has a better grounding dispersion effect when it is impacted by lightning current, the internal temperature is lower, the thermal stress is smaller, and it has better electrothermal characteristics, which is more suitable for the field of power system grounding engineering without laying grounding body.