Abstract: Aiming at the shortcomings of existed methane detection device of coal mine,the paper(proposed) a design scheme of methane infrared detection system of coal mine based on detection principle of spectral absorption.It analyzed detection principle of infrared difference absorption,and introduced design of hardware and software of the system in details.The methane infrared detection system of coal mine took wide band LED as light source and used one light path to realize detection of difference absorption,which eliminated error caused by difference of light path in two light path system,used phase locking amplifier to make phase sensitivity demodulation for small signal and moving smoother method with removing extreme value to filter for digital quantity,which improved sensitivity of the system.The experimental result showed that the precision and stability of methane concentration detected by the system could meet detection demands.