The invention provides a niobium-doped bismuth oxybromide catalyst and a preparation method and a use method thereof. The preparation method comprises the following steps: 1, heating an alcohol solvent until the alcohol solvent is boiled, and naturally cooling, 2, sequentially adding a bismuth salt compound, a niobium compound and a bromine compound, mixing and fully stirring, 3, adding a neutralsolution, 4, carrying out high-pressure constant-temperature reaction, and 5, cooling to room temperature, carrying out centrifugal separation, respectively washing with water and an ethanol solution,drying, and collecting the powder to obtain the flower-ball-shaped niobium-doped bismuth oxybromide. The photocatalyst prepared by the preparation method disclosed by the invention is Nb-BiOBr, the photocatalyst has good visible light photocatalytic degradation organic matter performance, higher photocatalytic activity and photo-induced electron hole separation efficiency, the degradation efficiency of the photocatalyst is 6.4 times that of BiOBr in the prior art, and the photocatalyst is environmentally friendly, harmless, low in price, controllable in method and easy to operate and has wideapplication prospects in the field of environmental pollution and governance.