The hydrogenated nano-crystalline silicon (nc-Si:H) films have attracted more attention for peoples, because of their novel structure and peculiar properties. The nc-Si: H films are prepared by the high purity hydrogen diluted methane as the reactive gases and actived at r. f. and d. c. double power sources, in a conventional plasma enhanced chemical vapor deposition (PECVD) system. The film samples have been studied by means of high-resolution electron microscopy, Raman scattering spectroscopy, scanning tunneling microscopy and other means. Based on the analysis of fabricated processes of the nc-Si: H films, a fractal growth model which called diffusion and reaction limited aggregation (DRLA) model was proposed. It is shown that results of computer simulation agree with the experimental results.