Graphene　quantum　dots　(GQDs)　are　recently　emerging　carbon　nanomaterials.　GQDs　have　been　recognized　as　attractive　electrochemiluminescence　(ECL)　luminophores,　owing　to　their　environmental　friendliness,　facile　preparation,　easy　labeling,　and　high　ECL　activity.　However,　in　terms　of　the　co-reactant　of　GQDs　ECL,　only　strongly　oxidative　S2O8　2−　has　been　well　studied　and　applied　in　GQD-based　ECL　sensing,　which　seriously　limits　the　application　of　GQD　ECL　sensors.　In　the　present　work,　we　found　that　the　commonly　used　reducing　reagent,　sulfite　(SO3　2−),　could　serve　as　a　new　type　of　co-reactant　of　GQD　ECL.　Moreover,　GQDs　exhibited　much　higher　ECL　activity　than　spherical　carbon　quantum　dots　when　using　SO3　2−　as　the　co-reactant,　owing　to　more　abundant　surface　states　of　GQDs.　Further　investigation　showed　that　GQD/SO3　2−　ECL　could　be　sensitively　quenched　by　H2O2　at　physiological　pH.　On　this　basis,　new,　green,　and　simple　ECL　chemical　and　biological　sensors　have　been　proposed　for　the　detection　of　H2O2　and　biologically　interesting　molecules　such　as　glucose.　Additionally,　the　ECL　reaction　and　sensing　mechanisms　have　also　been　studied　and　discussed.　©　2017　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim