Novel TiO2/ZnO core-shell thin film has been deposited onto a glass substrate by the chemical bath deposition technique. The films were annealed in the temperature range of 373k and 673K in order to investigate the effect of annealing on the optical properties and thickness of the film. The films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM),Rutherford backscattering (RBS) and spectrophotometer. Our results showed that there is more crystallization and more orientation of the crystal growth with increase in temperature. The results also revealed that most of the optical properties were significantly affected by the annealing process. The calculated thickness shows that the films are nanocrystalline in nature. The optical band gap decreased with increase in temperature and are in the range of 2.17eV- 2.68eV.