Abstract: Adding a small mass flow rate of inert gas into the air arc flow field does not affect the performance evaluation of the thermal protection materials. In order to obtain the flow field characteristics of the inert gas-air hybrid arc, the flow field parameters of the supersonic nozzle exit were studied by controlling the arc current and inert gas mass flow rate in an arc heated wind tunnel. The experimental results show that the enthalpy and stagnation point heat flux of the helium-air hybrid arc are 6.07% and 1.02% higher than that of the air arc flow field respectively under the condition of helium mass ratio of 11.46%, total mass flow rate of 0.2 kg/s and arc current of 1300 A; the enthalpy and stagnation point pressure of the hybrid arc with inert gases such as neon, argon and krypton are lower than that of the air arc at the exit of the supersonic nozzle, and increase with the increase of mixed gas flow rate and arc current. The increase degree is related to the proportion of the added gas medium and total mass flow rate.