Two sets of μc-Si : H films as a function of pressure were fabricated by very-high-frequency plasma enhanced chemical vapor deposition (VHF-PECVD). Deposition rate, Raman crystallinity, and photo/dark conductivity were investigated under both low and high power conditions. A plasma fluid model and a surface hydride-dependent precursor diffusion model were constructed to understand the evolution of microcrystalline silicon under low and high power conditions. Silyl, hydrogen, ion flux, silyl surface diffusion length are believed to have much influence on film growth rate, crystallinity and photo electronic properties. But the interesting point is that under a certain condition one or more of these parameters dominate μc-Si : H growth, while other parameters have weak influence. Short-life radicals are found to be the possible major factor on the deterioration of photo sensitivity of μc-Si : H films.