ZnS is one of the most important semiconductors with wide direct band-gap (3.68 eV) and it is widely used as electroluminescence, flat panel display and cathode ray luminous materials. Uniform ZnS optical thin films were deposited on Si (111) substrates by a vacuum evaporation method. The influences of evaporation temperature, deposition time and the distances between substrates and evaporation sources on the phases and morphologies of the ZnS thin films were investigated. The as-prepared thin films were characterized by X-ray diffraction and atomic force microscopy. Results show that the as-prepared thin films are composed of sphalerite ZnS with a little wurtzite phase. The obtained thin films exhibit an oriented epitaxial growth along (111) direction. The evaporation temperature has a great effect on the phases and morphologies of ZnS thin films. Uniform ZnS thin films can be achieved at the evaporation temperature of 1200°C for 30 min. The crystallization of ZnS thin films improves with the increase of evaporation time.