The invention discloses a visible-light-driven photocatalyst C@Bi2O3-BiOBr-BiOI as well as a preparation method and an application thereof in sterilization. The preparation method of the catalyst comprises the following steps: (1) preparing nano carbon spheres by using glucose through a hydro-thermal reaction method; (2) stirring and dissolving Bi(NO3)3.5H2O in a glycol solution, performing dispersion by using anhydrous ethanol, adding the nano carbon spheres, stirring the mixture severely, performing ultrasonic dispersion, transferring the mixed solution into a polytetrafluoroethylene reaction kettle, and performing a hydro-thermal reaction for a period of time; and (3) cooling the mixture to a room temperature, adding cetyl trimethyl ammonium bromide (CTAB) and KI, adjusting the pH value, performing stirring continuously, performing centrifugal separation, then performing washing by using water and ethanol for a plurality of times, and then performing vacuum drying to obtain the C@Bi2O3-BiOBr-BiOI. The photocatalyst disclosed by the invention is low in preparation cost, makes use of visible light, saves energy sources, and has an excellent sterilization ability.