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Traditional anaerobic bioprocesses failed to achieve the efficient biotransformation of nitrobenzene, graphene-anaerobic sludge composite as a novel biocatalyst was proposed for the enhancement of nitrobenzene biotransformation.Graphene/anaerobic sludge composites (RGO/AS) with good settling performance were formed when GO was added in anaerobic sludge (AS) system for 24 h cultivation.The presence of RGO promoted nitrobenzene bioreduction by anaerobic sludge and the highest removal efficiencies of nitrobenzene were observed in amendments with initial ratio GO (3-5μm) vs sludge of 0.075.Dehydrogenase(DHA) activity in RGO/AS increased approximately 1.6-fold than AS system and the redox active species were produced in RGO/AS supematant.The increased acetate to propionate ratio was observed in RGO/AS during glucose fermentation, and that nitrobenzene biotransformation by both AS and RGO/AS was independent of methanogenesis, but dependent on acetogenesis.Moreover, bound EPS and free EPS from RGO/AS is involved in direct bioreduction of nitrobenzene and also bound EPS interact with secreted redox active species mediated nitrobenzene bioreduction by extracellular electron transfer.