A batch of TiO ₂films with different Zn ²⁺compositions are prepared on a single crystal silicon substrate by using sol-gel method to observe the changes in optical and photocatalytic properties in the alloying process of Zn ²⁺and TiO ₂. X-ray diffractometer (XRD) is used to observe the changes in the crystal structures of the films in the alloying process and to track the formation of ZnTiO ₃compounds. Scanning electron microscope (SEM) and atomic force microscope (AFM) are used to observe the phenomena of a large number of holes on the surfaces of the films due to the limited solubility of the crystal lattice for Zn ²⁺in the alloying process. X-ray photoelectron spectroscopy (XPS) and optical bandgap are used to observe the changes at a level of the electronic structure of the films in the alloying process of Zn ²⁺with TiO ₂. Finally, by degrading the methylene blue solution, it is shown that a small amount of Zn ²⁺doping is completely dissolved in TiO ₂, destroying the TiO ₂crystalline quality. As the compositional share of Zn ²⁺continues to increase to 15%, the limited solubility of TiO ₂for Zn ²⁺is verified in the XPS peak fitting, resulting in a large number of hole structures in the film, and the active specific surface area of the film is enhanced, while Zn ²⁺effectively traps the photogenerated e ^–/h ⁺. In order to continue to observe the effect of Zn ²⁺concentration on TiO ₂, we increase the concentration of Zn ²⁺to 40% and observe the phenomenon in the alloying process of Zn ²⁺with TiO ₂. It is shown that the appearance of the compound ZnTiO ₃can act as a complex center for e ^–/h ⁺and a significant decrease in the percentage of TiO ₂leads to a gradual decrease in the photocatalytic efficiency of the films after alloying.