Cu2+　ions　play　essential　roles　in　various　biological　events　that　occur　in　the　human　body.　It　is　important　to　establish　an　efficient　and　reliable　detection　of　Cu2+　ions　for　people＇s　health.　The　solution-gated　graphene　transistors　(SGGTs)　have　been　extensively　investigated　as　a　promising　platform　for　chemical　and　biological　sensing　applications.　Herein,　highly　sensitive　and　highly　selective　sensor　for　Cu2+　ion　detection　is　successfully　constructed　based　on　SGGTs　with　gate　electrodes　modified　by　functional　carbon　quantum　dots　(CQDs).　The　sensing　mechanism　of　the　sensor　is　that　the　coordination　of　CQDs　and　Cu2+　ions　induces　the　capacitance　change　of　the　electrical　double　layer　(EDL)　near　the　gate　electrode　and　then　results　in　the　change　of　channel　current.　Compared　to　other　metal　ions,　Cu2+　ions　have　an　excellent　binding　nature　with　CQDs　that　make　it　an　ultrahigh　selective　sensor.　The　CQD-modified　sensor　achieves　excellent　Cu(2+　)ion　detection　with　a　minimal　level　of　concentration　(1　x　10(-14)　M),　which　is　several　orders　of　magnitude　lower　than　the　values　obtained　from　other　conventional　detection　methods.　Interestingly,　the　device　also　displays　a　quick　response　time　on　the　order　of　seconds.　Due　to　the　functionalized　nature　of　CQDs,　SGGTs　with　CQD-modified　gate　show　good　prospects　to　achieve　multifunctional　sensing　platform　in　biochemical　detections.