By using the tunable diode laser absorption spectroscopy(TDLAS) technology the absorption line of methane at the wavelength of 1 653.72 nm is found to be free of interference and suitable for the measurement of coal mine methane.The high performance microcontroller(DSP) and second harmonic detection are used to lower the detection limit further that is below 0.074 mg/m3.It has an obvious advantage in sensitivity and stability and can achieve real-time measurement of the coal mine methane.