The utility model relates to a double wavelength difference methane concentration sensor which comprises a light source, an optical processing module, a signal processing module and a signal analysis module, wherein the light source is used for transmitting an optical signal; the optical processing module comprises a photoelectric detector and is used for filtering the optical signal emitted by the light source so as to enable a group of optical signals with the first wavelength and a group of optical signals with the second wavelength to pass through, and to enable the two groups of optical signals periodically and respectively to be transmitted to the photoelectric detector by means of gases to be detected, and the photoelectric detector converts the optical signals into electric signals; the signal processing module is used for filtering and amplifying the electric signals output by the optical processing module; and the signal analysis module is used for analyzing the electric signals output by the signal processing module.