Non-metallic graphene oxide (GO) and carbon nanodots (CDots) co-doped BiOI ternary system (GO/CDots/BiOI) was successfully synthesized via a simple one-step solvothermal process. The compositional characterization, optical and electrical properties of photocatalysts were investigated in detail. The prepared ternary photo catalysts possessed the excellent visible-light driven photocatalytic 4-chlorophenol (4-CP) degradation. Additionally, the 4-CP removal efficiencies decreased in the order of GO/CDots/BiOI (98.2%) > CDots/BiOI (89.9%) > GO/BiOI (78.5%) > pristine BiOI (41.7%) in 3 h under visible light irradiation. The dissolved organic carbon (DOC) removal and the dechlorination efficiency by the GO/CDots/BiOI were 66.3% and 85.2%, respectively, much higher than pristine BiOI. The co-existence of GO and CDots on the BiOI greatly promoted visible light harvesting and utilizing ability and inhibited the recombination of photogenerated electron/hole pairs. The synergistic effect between GO, CDots and BiOI was expounded, and the photocatalytic reaction mechanism was proposed in detail via the band structure analysis and free radical trapping experiments.