In order to improve the catalytic property of Fe-based Fenton catalysts, a sulfur-modified Fe3O4 coating Fenton-like catalyst was successfully prepared on titanium alloy via plasma electrolytic oxidation. The effect of the concentration of iron source K3[Fe(CN)6] in the electrolyte on the structural composition and phenol degradation performance of the coating was studied. In addition, the surface morphology and phase composition of the catalyst were characterized by SEM, EDS and XRD, and phenol was used as the target degradation product to evaluate the Fenton-like catalytic activity. Results showed that when the concentration of K3[Fe(CN)6] in the electrolyte increased, the Fe3O4 composition in the film increased, the sulfur-containing groups decreased, and the pore size and number of pores on the surface of the coating also changed. Phenol degradation experiments displayed that the sulfur-modified Fe3O4 coating had good catalytic activity under near-neutral conditions.