Abstract: In this study, Au/g-C₃N₄ composite nanomaterials were prepared and characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM) and ultraviolet-visible diffuse reflectance (UV-Vis DRS). The photocatalytic degradation of ochratoxin A (OTA) by Au/g-C₃N₄ composite nanomaterials under different factors was compared and the photodegradation mechanism was investigated. Adsorption equilibrium experiments were carried out under visible light irradiation to studythe photocatalytic properties of the materials, and the effects of the concentration of AuNPs and the amount of Au/g-C₃N₄ on the photocatalytic efficiency were also studied. The results showed that the Au/g-C₃N₄ composite nanomaterials were successfully prepared, with AuNPs uniformly distributed on the surface of graphitic carbon nitride (g-C₃N₄). The photocatalytic degradation experiments showed that the OTA degradation rate could reach 95.84% after 180 min of irradiation with a xenon lamp (500 W) under the optimal conditions with an initial concentration of 5 μg/mL of OTA and 2 mg/mL of Au/g-C₃N₄ catalyst. Repeatability experiments revealed that the Au/g-C₃N₄ composite nanomaterials could be reused, and the degradation efficiency could still remain at 85.82 % after 5 times. The free radical trapping experiments confirmed that ·O₂⁻ and h⁺ played a dominant role in the photocatalytic degradation of OTA by the Au/g-C₃N₄ catalyst. This study could provide important theoretical support for the development of highly effective catalyst for the detection of OTA.