Graphene　(GR)-CdS　nanocomposites　with　different　weight　addition　ratios　of　GR　have　been　assembled　by　a　facile　solvothermal　treatment.　The　GR-CdS　nanocomposite　photocatalyst　with　an　appropriate　ratio　of　GR　exhibits　enhanced　photoactivity　for　selective　reduction　of　aromatic　nitro　compounds　to　the　corresponding　aromatic　amines　in　water　under　visible　light　irradiation　as　compared　with　blank-CdS.　The　characterization　of　GR-CdS　nanocomposite　photocatalysts　by　a　collection　of　techniques　discloses　that:　i)　GR　can　tune　the　microscopic　morphology　of　CdS　nanoparticles　and　improve　light　absorption　intensity　in　the　visible　light　region;　ii)　GR　scaffolds　act　as　an　electron　reservoir　to　trap　and　shuttle　the　electrons　photogenerated　from　CdS　semiconductor　under　the　visible　light　illumination;　iii)　the　introduction　of　GR　enhances　the　adsorption　capacity　of　GR-CdS　nanocomposites　toward　the　substrates,　aromatic　nitro　compounds.　The　synergistic　effect　of　these　factors　should　account　for　the　photoactivity　advancement　of　GR-CdS　nanocomposites　toward　the　probe　reactions.　Furthermore,　because　the　photogenerated　holes　in　the　system　are　trapped　by　the　quenching　agent　ammonium　oxalate,　the　as-obtained　GR-CdS　photocatalyst　is　stable　during　the　photocatalytic　reduction　reactions.　A　reasonable　model　has　also　been　proposed　to　illustrate　the　reaction　mechanism.　©　2014　Dalian　Institute　of　Chemical　Physics,　the　Chinese　Academy　of　Sciences.　Published　by　Elsevier　B.V.