SrTiO3 has great potential for applications in the photoelectrochemical cathodic protection field due to its suitable band structure and stable recombination characteristics, but the low utilization of sunlight and high recombination rate of photogenerated electron-hole pairs limit its further development. Based on this, SrTiO3 was modification by doping anion (F) in order to obtain a new kind of SrTiO3 photoanode material with efficient and stable photoconversion performance. F-doped SrTiO3 photoanodes with different F doping concentrations were prepared by solvent thermal method. UV-Vis DRS and fluorescence spectrometer test results show that F doping improves utilization of sunlight and separation ability of photogenerated electron-hole pairs. The photoelectrochemical cathodic protection results are as follows: when F doping concentration is 2.0% (atomic fraction), the photocurrent density of F-2.0%-SrTiO3 coupled with 304 stainless steel reaches 3.7 μA/cm2, and the open-circuit potential of 304 stainless steel negatively moves to -0.42 V under light conditions, showing an effective protection for 304 stainless steel in simulated seawater.