The energies, atomic Mulliken charges, and electronic structures of Zn adsorbed on the pure surface, and on the surfaces with an oxygen vacancy (Zn-TiO2-VO) and one hydroxyl group (Zn-TiO2-VO-OH) are investigated by density functional theory, plane-wave pseudo-potential method, and the most stable surface structures (namely model (c), model (aI), and model (aII) are found. The results indicate that firstly, Zn interacts mainly with the surface oxygen by Zn–O covalent bond; secondly, when Zn atoms are adsorbed on the defective surface, the adsorption energy is reduced down to -1.75 eV, showing that Zn atoms are prone to being adsorbed on the oxygen vacancy surface. Finally, although no impurity states are introduced in to the gap when the Zn atoms are adsorbed to the surface with hydroxyl group, the band gap is reduced down to a minimum (1.85 eV), which is expected to improve the photocatalytic activity of TiO2.