The interaction of water molecule and a ceria (111) surface was investigated using DFT+U (density functional theory with the inclusion of on-site Coulomb interaction by introducing Hubbard U parameter) method. The results showthat water molecules adsorb on the oxidized ceria (111) surface through a single H-bond configuration and they do not decompose. On a reduced ceria (111) surface, the water molecules adsorb through a non-H-bond configuration. Furthermore, water molecules prefer to dissociate and form a hydroxyl surface. The hydroxyl surface is much more stable than the physisorption state of H2 on the oxidized ceria (111) surface. In other words, reoxidation of the reduced ceria (111) surface through the dissociation of the hydroxyl surface and the generation of H2 molecules is an endothermic process. Therefore, there are mainly two adsorption states for water molecules on the reduced ceria (111) surface: i) chemisorption through a non-H-bond configuration and ii) dissociative adsorption with a hydroxyl surface. The hydroxyl surface may dissociate under certain conditions and reoxidize the reduced ceria (111) surface.