Intrinsic　hydrogenated　microcrystalline　silicon　(mu　c-Si:H)　films　have　been　prepared　by　hot-wire-assisted　microwave　electron-cyclotron-resonance　chemical　vapour　deposition　(HW-MWECR-CVD)　under　different　deposition　conditions.　Fourier-transform　infrared　spectra　and　Raman　spectra　were　measured.　Optical　band　gap　was　determined　by　Tauc　plots,　and　experiments　of　photo-induced　degradation　were　performed.　It　was　observed　that　hydrogen　dilution　plays　a　more　essential　role　than　substrate　temperature　in　microcrystalline　transformation　at　low　temperatures.　Crystalline　volume　fraction　and　mean　grain　size　in　the　films　increase　with　the　dilution　ratio　(R=H-2/(H-2+SiH4)).　With　the　rise　of　crystallinity　in　the　films,　the　optical　band　gap　tends　to　become　narrower　while　the　hydrogen　content　and　photo-induced　degradation　decrease　dramatically.　The　samples,　were　identified　as　mu　c-Si:H　films,　by　calculating　the　optical　band　gap.　It　is　considered　that　hydrogen　dilution　has　an　effect　on　reducing　the　crystallization　activation　energy　of　the　material,　which　promotes　the　heterogeneous　solid-state　phase　transition　characterized　by　the　Johnson-Mehl-Avrami　(JMA)　equation.　The　films　with　the　needed　structure　can　be　prepared　by　balancing　deposition　and　crystallization　through　controlling　process　parameters.