The　effect　of　light-induced　thermal　annealing　at　low　temperature　on　the　structure　and　electronic　properties　of　hydrogenated　amorphous　silicon　(a-Si:　H)　as　a　function　of　annealing　conditions　was　studied　by　FTIR　spectra　method.　The　deposition　of　a-Si:　H　films　was　performed　by　using　microwave　electron　cyclotron　resonance　(MW　ECR)　plasma　with　the　assistance　of　tungsten　filament.　In　this　study,　the　infrared　spectroscopy　results　show　the　interesting　changes　under　the　different　annealing　condition.　The　increase　in　the　transmission　coefficient　at　both　630　and　2000　cm-1　indicates　that　bonded　hydrogen　moved　and　effused　from　the　amorphous　network.　The　bond-centered　(BC)　H　diffusion　model　is　used　to　explain　the　H　elimination　phenomenon,　we　argue　that　the　BC　H　atoms　formed　by　the　nonradiative　recombination　of　photo-induced　carriers　and　the　exchange　between　BC　H　and　deeply　trapped　H　produce　more　and　more　BC　H　atoms,　the　BC　H　atoms　will　recombine　each　other　and　form　molecular　hydrogen,　the　process　of　H　elimination　is　prior　to　monohydride　clustering　and/or　bonds　switching.