Abstract: For the current methane sensors used in coal mines, there are problems of low precision, poor stability and being susceptible to other gases,a laser sensor based on harmonic detection is designed,and the basic principle of TDLAS is analyzed in detail.The overall design of sensor system,laser and control circuit,photoelectric conversion and preamplifier circuit,RS485 circuit,frequency signal circuit and system software design are introduced emphatically.At the same time,the catalytic methane sensor,infrared methane sensor and laser methane sensor are respectively introduced into the standard methane gas sample and diesel vehicle exhaust gas for measurement.The results show that the laser methane sensor has the advantages of high detection accuracy,small error and no interference from cross-gas.In accordance with the requirements of the National coal mine safety standards, it can further ensure the safe production of coal mines.