Abstract: According to the disadvantages of gas concentration detection technology in coal mine, dual-light path and dual-wavelengths methane concentration detector was designed by using differential absorption technology. Voltage of detector was measured with different gas concentration in laboratory environment, from which fitting curves of the voltage and gas concentration can be obtained, experiment result shows that measurement error is less than 1.8%, and the system has very high measurement precision which can meet the requirements of the methane concentration detection in coal mine.