In this paper, the geometries and properties of H2S and its decomposition fragments adsorbed on Fe(111) surface are studied by means of the density functional theory based on generalized gradient approximation in wide ranges of coverage; the adsorption energy, work function, charge density difference, density of states, and charge population are calculated; the effect of coverage on surface adsorption is discussed; the adsorbability values of H2S, HS radical and S on Fe(111) are compared and analyzed. The results show that the force between absorbates and surface gradually weaken as the coverage increases, the interactions between the above-mentioned particles and Fe(111) are compared with each other: the magnitudes of their interactions are in the order of H2SxSy corrosion product films are easily formed, and the compactnesses of corrosion product films change with coverage variation. A study of the adsorbability values of various adsorbates in low index crystal plane indicates that the interactive force between adsorbates and Fe(111) surface is strongest, and that between the Fe(100) surface and Fe(110) is relatively weak, the difference in adsorption energy between them is not so much.