Gas concentration is an important factor endangering production safety in petrochemical and coal mining operations,so it is necessary to achieve rapid and accurate concentration detection for this gas through scientific means.The detection of underground coal mines gas concentration was taken as the research object,the working principle of the optical fiber gas sensor was discussed,and the underground gas concentration monitoring system was designed based on the optical fiber gas sensor.Through simulation experiment and actual measurement,it is verified that the designed system has high sensitivity and fast response speed,and it is suitable for gas concentration detection under harsh working conditions.