A novel ternary nanocomposite photocatalyst, Ag-BiOI- reduced graphene oxide (rGO), driven by visible light was successfully synthesized with hydrothermal strategy. XRD, SEM, TEM, HRTEM, EDS, raman spectroscopy, XPS, DRS, photocurrent and EIS analysis were employed to characterize all synthesized compounds. Compared to pure BiOI, Ag-BiOI and BiOI-rGO, the 5？mol% Ag-BiOI-rGO 5？wt% displayed superior photocatalytic capability with complete removal of diclofenac (10.0？μg？mL？1) in 80？min under visible light. The characterization results indicated that the addition of Ag and rGO enhanced the charge separation and suppressed the recombination of photogenerated electrons and holes, which upgraded the ability of Ag-BiOI-rGO to degrade diclofenac compared with BiOI. Six reaction intermediates of diclofenac were detected by LC-MS/MS, subsequently, two degradation routes were proposed. This work provides a promising strategy to fabricate more effective photocatalysts to deal with organic pollutants in wastewater.