Methane　is　a　flammable　and　explosive　gas,　which　is　the　main　component　of　mashgas　and　natural　gas.Methane　monitoring　plays　an　important　role　in　coal　mine　safety　and　natural　gas.The　high-Q　whispering　gallery　mode　(WGM)　of　optical　microcavity　has　a　long　photon　lifetime,　which　greatly　prolongs　the　effective　optical　path　between　light　and　surroundings,and　has　the　potential　to　be　made　into　miniaturized　and　highly　sensitive　gas　sensor　device.In　order　to　realize　the　high　Q　microcavity　WGM　enhancement　light　absorption　methane　gas　sensor,the　key　technology　is　to　lock　the　resonant　frequency　of　the　microsphere　cavity　to　the　DFB　laser　frequency.In　order　to　ensure　the　intrinsic　safety　of　the　CH4　sensor,　the　resonance　wavelength　of　the　all-optically　tuning　microsphere　cavity　was　studied,　so　that　it　was　locked　to　the　wavelength　of　the　CH4　absorption　peak　of　1653.72nm.　The　resonant　wavelength　of　the　microsphere　was　tuned　by　injecting　light　along　the　fiber　handle　of　the　microsphere,　and　the　refractive　index　of　the　microsphere　was　changed　by　absorbing　light　and　converting　heat　with　the　coating　of　the　sphere　crown.　©　Published　under　licence　by　IOP　Publishing　Ltd.