Abstract: In order to improve the utilization of CaCO₃ and expand its application in pollutant treatment and antibacterial, Ag₂O was synthesized by precipitation method and CaCO₃ was added to further prepare CaCO₃/Ag₂O photocatalyst. The structural composition and morphological lattice were characterized by XRD, XPS, SEM, TEM. The experimental results show that when the molar ratio of CaCO₃ to Ag₂O is 1∶1, the degradation rate of methylene blue can reach 90% within 30 min under visible light. The subsequent four cycle experiments also show that the CaCO₃/Ag₂O composite photocatalyst has good stability. The antibacterial test of photocatalyst shows that the CaCO₃/Ag₂O composite photocatalyst can completely eliminate Staphylococcus aureus within 30 min. Ag₂O supported by CaCO₃ forms a heterojunction, which promotes the separation of photogenerated electron-hole pairs and effectively improves the photocatalytic performance of the composite system.