Doxycycline (DC) is an antibiotic that exists in the environment and urgently needs to be effectively removed. Herein, the light/BiVO4@Ag2O/H2O2 system and light/BiVO4@Ag2O system were constructed to achieve effective degradation of DC. Under the same degradation conditions, the efficiency and mechanism of two systems on DC degradation were compared. The results showed that the removal rate of DC in light/BiVO4@Ag2O/H2O2 system was better than that in light/BiVO4@Ag2O system. The optimal pH ranges were 3.5–9.5 and 7.5–9.5 for light/BiVO4@Ag2O/H2O2 and light/BiVO4@Ag2O systems, respectively. The optimal water temperatures were both 35 °C in two systems. The optimal BiVO4@Ag2O dosages were both 182 mg/L. The Cl−, SO42-BrO3-NO3-PO43- and SO42-BrO3-NO3-PO43- had promoting effects on DC removal, while SO42-BrO3-NO3-PO43- and SO42-BrO3-NO3-PO43- had inhibitory effects on DC removal. The capture experiment showed that h+, ·O2− and ·OH existed in two degradation systems, among which h+ played an important role. Analysis of degradation intermediates showed that the proportion of smaller molecules in light/BiVO4@Ag2O/H2O2 visible light system was higher than that in light/BiVO4@Ag2O visible light system, indicating that oxidation active substances were more easily produced in light/BiVO4@Ag2O/H2O2 system.