Nanocrystalline silicon films have been fabricated from SiH4 diluted with H2 in very high frequency (40.68 MHz) plasma enhanced chemical vapor deposition system at low temperatures (250oC). The influence of pressure on the structural properties of nanocrystalline silicon films has been investigated. The experimental results reveal that a very high hydrogen dilution is needed to crystallize the film grown at high pressure. If the hydrogen dilution is not high enough, the film could also be crystallized through lowering the pressure. Furthermore, the crystallinity and grain size increase with decreasing the pressure. These results could be attributed to the increase of ion bombardment energy and the higher atomic hydrogen flux toward the growing film surface at lower pressures.