The highly active Mn-doped Ag3PO4 photocatalyst was successfully synthesized under coprecipitation method using AgNO3, Na2HPO4.12H(2)O, and MnSO4.H2O, followed by annealing. The products were characterized using the SEM, XRD, DRS, XPS, and BET. The results showed that the Mn doping decreased the broad absorption in the visible region and increased the atomic ratio of O/Ag. The hydroxyl defects and oxygen vacancies can be sup pressed by Mn doping and the photocatalytic activity under visible light irradiation could be improved. This excellent photocatalytic activity was caused by decreasing the recombination of electron and holes due to suppressing the defect sites in the surface of Ag3PO4.