First-principles calculations and thermodynamics analyses were combined to study the surface stabilities of 3C-SiC and H2O adsorption on the (110) surface. The stoichiometric (110) surface was predicted to be generally the most stable. Only at the extremely C-poor condition, the nonstoichiometric Si-terminated (100) could become more energetically favored. The adsorption and dissociation of single H2O molecule on the 3C-SiC (110) were then comparatively investigated. Calculations show that H2O molecules prefer to partially dissociate into one hydroxyl OH and one H adsorbed at the top-most Si and C sites, respectively, leading to the formation of a hydrogen network on the surface. The calculated equilibrium adsorption diagram further suggested that the 3C-SiC (110) surface can be only either completely clean or fully covered by the partially dissociated species of H2O, for a wide range of temperature and the partial potential of H2O.