Abstract: Integrating thermal distribution and constant temperature difference modes, a high-precision, wide range, and fast response gas flow sensor was designed based on a domestic thermal flow measurement chip to optimize the volume and accuracy of gas flow sensor for respiratory monitoring. Firstly, a driver amplifier circuit was designed for the thermal flow measurement chip, and the PCB was plotted and processed to make the sensor analog output 0.5~4.5 V under the respiratory flow monitoring range −200~200 L/min. Secondly, a gas flow channel structure with branches and a well waterproof packaging structure were designed for the sensor to meet the high humidity environment requirements of medical respiratory monitoring. Finally, the assembly test of the overall sensor was completed, and the sensor parameters were calibrated. The experimental results show that the overall power of the sensor can reach 20 mW, the flow measurement error can be low ± 1% F.S., the response time is less than 15 ms, and the linearity tolerance is less than ± 3%.