This　work　is　to　construct　an　electrochemiluminescent　(ECL)　sensor　with　improved　accuracy　for　the　detection　of　Cu2+.　The　improved　accuracy　is　achieved　by　utilizing　a　reaction　system　to　realize　Cu2+　dose-dependent　dual　suppression　of　ECL　recovery　from　gold　nanoparticle-graphitic　carbon　nitride　nanosheet　naonohybrid　(Au-CNNS)　film.　The　ECL　sensor　shows　sensitive　response　to　Cu2+　in　the　concentration　range　of　5　nM　to　500　nM　with　an　enlarged　slope,　and　high　specificity　attributed　to　the　high　affinity　of　CNNS-Cu2+　complex　and　the　high　catalytic　activity　of　Cu(NH3)(6)(2+)　to　decompose　H2O2　in　the　reaction　system.　The　proposed　ECL　sensor　with　improved　accuracy　may　prove　valuable　in　future　biomedical　applications.