Low　electrode　resistance　is　crucial　for　achieving　efficient　reactions　in　bio-electrochemical　system　(BES),　especially　considering　the　factors　of　BES　scaling-up　and　microbial　effects.　Graphene　has　revealed　a　cornucopia　of　potential　applications　due　to　its　high　conductivity　and　extraordinary　electrochemical　properties.　Here,　significant　reduction　of　electrode　resistance　and　increment　of　electrochemical　activity　were　achieved　by　fabricating　the　three-dimensional　carbon　brush　using　reduced　graphene　oxide　(rGO/carbon　brush)　through　one-step　electrodeposition　without　any　binder.　The　rGO/carbon　brush　was　employed　as　cathode　in　BES　equipped　with　bio-anode　for　azo　compound　(AO7)　removal.　The　charge　transfer　resistances　of　cathode　part　and　whole　cell　were　decreased　by　89%　and　65%,　respectively.　The　reactor　showed　quickly　start-up　within　48　h　with　peak　cycle　current　six　fold　increase　relative　to　the　control.　AO7　decolorization　efficiency　reached　91.1　+/-　0.1%　at　4　h　and　97.6　+/-　0.4%　at　6　h.　Effective　decolorization　of　AO7　was　at　rate　up　to　650.7　g　AO7/m(3).h.　The　results　indicated　that　the　advantages　of　graphene　and　three-dimensional　carbon　brush　successfully　improved　the　overall　performance　of　BES　and　enhanced　refractory　pollutants　removal　when　applied　to　specific　wastewater.