A　novel,　highly　sensitive　and　selective　colorimetric　method　for　copper(II)　detection　through　copper(I)　catalyzed　alkyne-azide　cycloaddition　reaction　(CuAAC)　has　been　developed.　Copper(I)　is　produced　by　the　electrochemical　reduction　of　copper(II)　via　Bulk　Electrolysis　(BE)　with　coulometry.　The　azide-and　alkyne-functionalized　Au　nanoparticles　(AuNPs)　can　aggregate　quickly　(10　min)　through　CuAAC　reaction,　resulting　in　the　color　of　the　solution　changing　from　red　to　purple.　Furthermore,　the　change　of　color　is　closely　related　to　the　concentration　of　copper(II),　and　1　nM　copper(II)　could　be　detected　by　the　naked　eye.　Additionally,　the　proposed　method　has　good　selectivity　to　copper(II)　in　the　presence　of　other　common　metal　ions.