Density functional theory is employed to investigate H2S adsorption on perfect, defect, step Pd(111) and Pd/gamma-Al2O3(110) surfaces at different coverage. The adsorption of one and two H2S molecules are completely dissociative adsorption on the Pd(111) surfaces; three H2S molecules adsorption is mixed adsorption on the prefect and defect Pd(111) surfaces, and completely dissociative adsorption on the step Pd(111) surface, while the most stable adsorption is partially dissociative adsorption on gamma-Al2O3(110) and Pd/gamma-Al2O3(110) surfaces. The adsorption energies of H2S on the defect and step Pd(111) surfaces are stronger than those on the perfect Pd(111) surface, and the existence of defect and step can enhance the H2S adsorption activity of Pd adsorbents at 0.11 ML. It is found that the gamma-Al2O3 supported single Pd atom reduces H2S adsorption activity at low coverage, and gamma-Al2O3 support enhances the activity of Pd for H2S adsorption at high coverage. The results show that the total adsorption energies increase as the coverage increases on Pd surfaces, and the stepwise adsorption energies decrease as the coverage increases. The stepwise adsorption energies show that the full monolayer H2S adsorption on the various surfaces is thermodynamically favorable. (C) 2017 Elsevier B.V. All rights reserved.