In order to meet the needs of synchronous analysis of methane gas in drilling fluid and realize the goal of methane gas measurement while drilling(MWD),a miniature infrared methane gas sensor for MWD is designed.First,the infrared absorption peak of methane gas was compared and analyzed with Hitran database to determine the center wavelength of the detector filter.Then the optical simulation software TacePro was used to analyze the light propagation direction of the cavity and the light intensity distribution of the two receiving surfaces of the detector,which can determine the rationality of the optical cavity design.Finally,the corresponding working circuit is designed according to the working principle of infrared gas sensor.Experimental results indicate that the detection accuracy of the sensor is better than 0.5% F.S.at room temperature and better than 0.8% F.S.at 120 ℃.The detection of trace methane gas in the saturated aqueous solution of methane can be realized at room temperature,which can meet the needs of methane gas measurement while drilling .This sensor has a wide application prospect in the field of oil drilling.