Dicyandiamide　(DICY)　is　a　common　ligand　that　exhibits　low　toxicity　but　can　irritate　the　skin　and　eyes　and　cause　methemoglobinemia　on　long-term　exposure.　Crystalline　Cu-dicyandiamide　(Cu-DICY)　was　obtained　via　facile　synthesis　and　its　molecular　structure　and　theoretical　Raman　spectra　were　simulated　by　using　density　functional　theory　(DFT).　The　results　suggested　that　the　Cu2+　coordinates　with　two　H2O　molecules　and　two　different　DICY　molecules　(an　imino　DICY　and　an　amino　DICY).　The　stability　constants　of　Cu-DICY　were　calculated,　and　the　electrochemical　properties　were　studied.　Two　electro-chemical　redox　processes　occur　in　Cu-DICY　in　an　aqueous　solution:　a　reversible　reaction　with　a　formal　potential　of　0.2　V　vs.　MSE　and　an　irreversible　reaction　between　–0.4　and　–1.2　V　vs.　MSE.　The　standard　rate　constant　k0　for　the　reversible　reaction　was　estimated　to　be　7.6×10–3　cm/s.　In　addition,　based　on　the　reversible　reaction　of　Cu-DICY,　square　wave　voltammetry　was　used　to　rapidly　determine　the　concentration　of　Cu(II)　and　the　detection　limit　was　66.7　μg/L,　which　satisfies　the　detection　limit　requirements　for　copper　in　tap　water　(2　mg/L)　as　provided　by　the　World　Health　Organization.　©　2018,　Science　China　Press　and　Springer-Verlag　GmbH　Germany,　part　of　Springer　Nature.