Abstract: From the basic principle of infrared spectrum absorption method, the high-precision gas concentration signal processing calculation method of the IR optical sensor was presented. This paper focused on the establishment of the gas concentration calculation model and experimental method for determining the various parameters. From the analysis of the principle of gas concentration calculation method, a new formula for gas detection was obtained by gradually modifying the Lambert-Beer law. The formula can be used to calculate gas concentration. To reduce the environmental temperature influence on the detection results of infrared gas concentration, temperature compensation was required. Through temperature compensation, the sensor can be used in various temperature conditions. After measurement, the sensor has good stability and realizes the 10010-6 distinguishing ability. It meets most occasions use requirement.