Abstract: A protonated graphite carbon nitride (P-g-C₃N₄) coated graphene oxide (GO) composite material (GO@P-g-C₃N₄) was prepared via electrostatic self-assembly method, and its application in photocatalytic antibacterial activities was investigated. The micro morphologyies, crystalline structures, and photoelectric properties of the GO@P-g-C₃N₄ composite material were characterized by SEM, TEM, XRD, XPS, Raman, UV-Vis DRS and steady-state/transient fluorescence spectroscopy (PL), etc. The structure of GO@P-g-C₃N₄ composite material was optimized by adjusting the content of P-g-C₃N₄. Under simulated solar light irradiation conditions, E. coli and S. aureus were used as experimental targets to study the photocatalytic antibacterial performance of GO@P-g-C₃N₄ composites with different P-g-C₃N₄ contents and the influence of irradiation times on antibacterial performance. It was found that GO@P-g-C₃N₄-80% composite material synthesized with a mass ratio of 1∶4 between GO and P-g-C₃N₄ exhibited antibacterial rates against E. coli and S. aureus of 98.80% and 95.99%, respectively after 100 min of illumination. After 150 min of illumination, antibacterial rates against both E. coli and S. aureus exceeded 99%, demonstrating significantly better antibacterial performance compared to individual GO or P-g-C₃N₄.