The application of near-infrared tunable diode laser spectroscopy(TDLAS) was investigated experimentally on gas detection, and the application on methane detection in coal mines with fiber sensor was presented. Based on gas absorption characteristics in near-infrared optical bands, with wavelength modulation on narrow-linewidth distributed feed back(DFB) laser, using harmonic detection technology, eliminating the effect of light source fluctuation and fiber jitter, the performance of measurement sensitivity is improved. By using the space division multiplexing(SDM) technology, a multi-point optical fiber sensor system for measuring methane is proposed. This method can reduce system costs, and will be adapted for requirement in harsh environments such as coal mines and so on.