The transition state calculation software CINEB was used to simulate the diffusion path and diffusion barrier of chlorine ion, after doping with different elements in rutile type TiO_2 film. The results show that the diffusion path A has larger holes and the adsorption of titanium and chlorine ions is weak, which makes the diffusion barrier of chlorine ions smaller, leading to the diffusion of chloride ion easier in path A. After Al element doping, aluminum atoms lose electrons and transfer to adjacent oxygen. Strong repulsion exists between chlorine ion and oxygen ion, result in the distortion of crystal structure and the slowly diffusion of chloride ion to improve corrosion resistance. After Mo doping, the 3 d orbital of Mo has a strong hybridization effect with the 2 P orbital of Cl, and there is a strong adsorption effect between Mo and Cl, making it difficult for chlorine ion to get out, so the corrosion resistance of material improved. The diffusion barrier of Al, Zr, Mo and Nb are high, which has a significant effect on the corrosion of titanium alloy. It is verified by experiments that Ti-5.5 Al-3.0 Zr-2.0 Sn-0.8 Mo-1.5 Nb has the minimum corrosion current and the best corrosion resistance, which is consistent with the calculated results.