Abstract: A kind of small size Schmidt-Boelter Gage was successfully developed for measuring heat flux in conventional hypersonic wind tunnel test. The simulation model of the Schmidt-Boelter Gage was built. The structure and size of the sensor were optimized based on the simulation model. According to the optimized results, the sensor with the size of Φ 3×10 mm was made and tested in the arc lamp heat flux calibration system. The results show that the size and performance of the developed sensor are comparable to the foreign sensor level. The sensitivity is greater than 30 μV·m²/kW, and the response time is about 50 ms.