Abstract: Hypersonic aircrafts need to endure extremely critical aerodynamic heating environment. Arc heated wind tunnels are the main facilities for ground assessment and filtration of thermal protection materials. Heat flux is one of the important simulation parameters of the arc heated wind tunnel, which needs to be measured accurately and effectively. Based on the characteristics of the flow in the arc heated wind tunnel, comparison measurement tests on heat flux of traditional slug calorimeter and coaxial thermocouple have been carried out. The numerical simulation on the heat transfer characteristics of the above two heat flux sensors has also been analyzed. For the plate free jet tests in arc heated wind tunnel with heat flux range of 0~1 100 kW/m², the heat flux test results of coaxial thermocouple are 10%~15% lower than those of slug calorimeter. The numerical simulation results indicate that the heat flux measurement value of the slug calorimeter is at least 10% higher, which is caused by the thermal physical parameters mismatch of its structure. While, the coaxial thermocouple has better measurement accuracy and the maximum measurement value deviation is only 2.19%. When coaxial thermocouple is used in the heat flux test models of different materials in arc heated wind tunnel, a stainless-steel sleeve of appropriate thickness should be added between coaxial thermocouple and models to meet the thermal matching of the surrounding environment beside the sensor.