Semiconductor photocatalysis has been considered as one of the most promising technologies for the removal of antibiotics from aqueous solutions. In this study, Ag2O/CeO2 p-n heterojuction photocatalysts were fabricated by an in situ loading Ag2CO3 on CeO2 spindles and subsequent via a thermal decomposition process. The Ag2O/CeO2 composites exhibited enhanced photocatalytic activity for the photodegradation of enrofloxacin (EFA) under visible light irradiation. A plausible degradation pathway for EFA was proposed. The Ag2O/CeO2 heterojuction photocatalysts exhibited the high mineralization ability towards the EFA molecule degradation based on three-dimensional excitation emission matrix fluorescence spectroscopy (3D EEMs) and total organic carbon (TOC) analysis. Transient photocurrent response, PL spectrum and EIS indicate high photoinduced charge separation efficiency possess in Ag2O/CeO2 composites. Active species trapping experiments and ESR technique confirmed that h(+) and center dot O-2 were the main active groups involved in photo-degradation of organic pollutants. Through the combination of various performance characterization and experimental results, a possible photo catalytic mechanism was proposed. Moreover, the energy band alignments of Ag2O/CeO2 heterostructure were calculated, which provided strong support for the proposed mechanism. This work could provide a new approach to construct new heterojunction photocatalysts and a deeper insight for the heterojunction catalyst.