Gas-filled switchgear is widely used in high altitude areas of China due to its wide adaptability and high reliability. Due to the reduction of atmospheric pressure in high altitude areas, the air cooling capacity is reduced, so the gas-filled switchgear in high altitude areas is more prone to the problem of high temperature rise. Taking a 12 kV gas-filled switchgear as the research object, a three-dimensional multi-physics coupling model is established for simulation research to explore the influence of altitude on the temperature rise characteristics of gas-filled switchgear under different load currents. The results show that when the switchgear is running at light load, it can work at any altitude. The switchgear in high-altitude areas should not be fully loaded, and should be operated with reduced capacity according to the situation. The gas flow rate near the circuit breaker and the incoming busbar in the cabinet is low, and it is easy to accumulate heat, so the optimization of heat dissipation should be considered. The research results can provide theoretical basis for improving the heat dissipation design of gas-filled switchgear used in high-altitude areas, thus improving the safe and stable operation level of gas-filled switchgear in high-altitude areas.