An optical fiber remote multiplexed sensing system of methane is designed based on the methane absorption spectroscopy characteristic, by taking the triangular signal to modulate the wavelength of the tunable diode laser. The laser wavelength shift is carried out adaptive adjustment by the built-in gas calibration pond to realize the locking of a methane absorption line. The methane concentration monitoring is realized in the range of 0-100%. The application tests are found in a garbage power generation plant and several coal mine ventilation air methane power generation plants. The results indicate that the monitor has good performances in stability and sensitivity and a long-term precision of 10ppm is achieved. It is possessed of wide application in Clean Development Mechanism (CDM) projects.