Basic principle of methane concentration sensor system was introduced. Methane concentration detection model of difference absorption structure based on orthogonal polarized light was presented. Mathematical model of methane concentration sensor was established. System structure of the sensor was designed and structure of optical path and gas chamber of the sensor was designed. Experimental research on the sensor was carried out. Using the polarizer, the sensor system transformed two difference wavelength monochromatic lights into orthogonal polarized lights, and then made the two orthogonal polarized lights pass the detection gas chamber simultaneously. Finally, the two monochromatic lights were separated by Wollaston prism, and light intensity signal of the two monochromatic lights was collected respectively by photodetectors. The experimental results show that the sensitivity and resolution of the sensor system were improved by using this method. The sensor has good linearity, stability, and strong anti-interference ability. This method has good detection effects.