Abstract: Based on the gas desorption rate method of coal, a CWH200 underground portable coal seam gas content rapid measurement instrument with a low-power microprocessor STM32F103RCT6 as the core control unit has been developed. The theoretical formula and overall design of the measuring instrument is introduced, and the hardware module principle and software flow of the measuring instrument is explained in detail. The two ranges automatically switch and can measure the coal seam gas content in the underground site within 10 minutes. The measurement results can be printed and uploaded in real time, which improves the measurement efficiency of coal seam gas content.