Temperature can affect the accuracy of tunable diode laser absorption spectroscopy (TDLAS) system. A system that can monitor temperature and methane in the same time is introduced. Two parameters are regulated by each other in order to increase accuracy not only in gas monitoring but also in temperature monitoring. The system uses 1653.7 nm as center wavelength of distributed feedback (DFB) laser, by taking the sawtooth signal to modulate the light frequency of the DFB laser. The scanning can obtain wavelength of fiber Bragg grating (FBG) and methane absorbing strength simultaneously. By wavelength scanning, the system can calculate temperature value and methane concentration. Temperature monitoring can regulate the deviation of methane detection caused by temperature changing, meanwhile, methane′s absorption line can locate the wavelength of FBG in order to make temperature monitoring more accurate. This temperature and methane monitoring system is more stable and reliable. It possesses wide applications in coal mine and methane extraction.