Hydrogenated microcrystalline silicon (mu c-Si:H) films were deposited by electron beam excited plasma (EBEP) CVD. As the SiH4, flow rate increases, deposition rate steeply increases, however, crystalline fraction and grain size decrease. A high deposition rate of 69 nm/min is achieved using SiH4 without H-2 dilution. It is shown that H atom plays key roll for mu c-Si:H formation. Results show that deposition mechanism of mu c-Si:H by EBEP is mainly controlled by the reaction in the plasma rather than the reaction on the film surface.