Abstract: Improving the separation efficiency of photogenerated carriers is an effective way to improve the protection performance of photoelectrochemical cathode. In order to make up for the shortcomings of SrTiO₃, such as large band gap and low separation efficiency of photogenerated carriers, BaTiO₃/SrTiO₃ composite films were prepared on fluorine-doped tin oxide conductive glass (FTO) by two-step ultrasonic spray pyrolysis process. The phase composition, surface morphology and optical properties of the samples were observed by XRD, SEM, UV-vis DRS and PL. Then, 304 stainless steel (304 SS) was used as the protected metal, and the photoelectrochemical cathodic protection performance of BaTiO₃/SrTiO₃ composite film was observed under the condition of shading light. The relative position of BaTiO₃/SrTiO₃ is determined by Mott-Schottky curve. The results show that the light absorption range of BaTiO₃/SrTiO₃ composite films prepared by two-step ultrasonic spray pyrolysis process is broadened to 400 nm. Compared with SrTiO₃ film, BaTiO₃/SrTiO₃ composite film has better light absorption performance. The separation efficiency of photo-generated carriers is improved. In 3.5wt%NaCl solution, BaTiO₃/SrTiO₃ composite film negatively shifts the open circuit potential of 304 SS to −0.38 V, with a negative shift degree of about 230 mV, while pure SrTiO₃ film can only negatively shift by 100 mV. The performance improvement is mainly attributed to the heterojunction formed by BaTiO₃ and SrTiO₃, which promotes the separation of photogenerated carriers.