Acinetobacter baumannii (A. baumannii) was widely existed in medical wastewater and easily induced infections to threaten the human healthy. We herein reported Ag/CoO-N photocatalyst composites for effective inactivation of A. baumannii. Ag/CoO-N composites were prepared by N-doping to CoO crystal in supercritical fluid followed with photo-reduction of Ag under visible-light irradiation. N-species was incorporated in the crystal structure of CoO, on which uniform Ag nanoparticles were stably deposited. Thus, the satisfactory photocatalytic sterilization of A. baumannii irradiated by visible-light irradiation was attributed to the high capability of light trapping and the efficient separation of photo-charges. Due to photo-induced electrons as the main active species, Ag nanoparticles and CoO-N synergistically realized mineralization of cell membrane, which lead K+ ions leak from cell to crack structure of bacteria, the decrease of genetic materials, and the cripple of the self-repair function in bacteria, resulting in the final cell death.