Abstract: The interaction of single, one layer, multilayer (two layer, three layer) water molecules with Au(100) surface was studied Using density functional theory, and the hydrophilic/hydrophobic properties of Au(100) surface were analyzed at atomic level. In addition, the hydrophilic/hydrophobic properties of the gold surface were revealed from the mesoscopic level through analyzing the wetting process of water droplets on the gold surface by molecular dynamics simulation. The results show that individual water molecules are physically adsorbed on Au(100) surface. Compared with a single water molecule, hydrogen bond interaction exists between one and multiple layers of water molecules, and the adsorption energy of one or multiple layers of water molecules is obviously higher than that of a single water molecule. The adsorption energy increases with the increase of the number of water layers. Molecular dynamics simulation results of water droplets on gold surface show that organic pollution has a great influence on the wettability of gold surface, resulting in a certain hydrophobicity of gold surfacewhile clean gold surface is hydrophilic.