Ultrathin Fe films were epitaxially grown on Si(111) by using an ultrathin iron silicide film with p(2 × 2) surface reconstruction as a template. The surface structure and magnetic properties were investigated in situ by low energy electron diffraction (LEED), scanning tunnelling microscopy (STM), and surface magneto-optical effect (SMOKE). Polar SMOKE hysteresis loops demonstrate that the Fe ultrathin films with thickness t＜ 6 ML (monolayers) exhibit perpendicular magnetic anisotropy. The characters of M-H loops with the exteal magnetic field at difference angles and the angular dependence of coercivity suggest that the domain-wall pinning plays a dominant role in the magnetization reversal process.