Copper(I)　species　can　be　acquired　from　the　reduction　of　copper(II)　by　ascorbic　acid　(AA)　in　situ,　and　which　in　turn　quantitative　catalyze　the　azides　and　alkynes　cycloaddition　reaction.　In　this　study,　propargyl-functionalized　ferrocene　(propargyl-functionalized　Fc)　has　been　modified　on　the　electrode　through　reacting　with　azide　terminal　modified　Au　electrode　via　copper(I)　catalyzed　azides　and　alkynes　cycloaddition　(CuAAC)　reaction.　The　electrochemical　impedance　spectroscopy　(EIS)　measurement　has　been　applied　to　test　the　electron　transfer　resistance　of　the　Au　electrode　before　and　after　click　reaction.　The　changes　of　the　fractional　surface　coverage　(theta)　with　different　AA　concentrations　are　characterized.　It　is　found　that　the　theta　value　has　a　linear　response　to　the　logarithm　of　AA　concentration　in　the　range　of　5.0　pmol/L　to　1.0　nmol/L　with　the　detection　limits　of　2.6　pmol/L　The　sensor　shows　a　good　stability　and　selectivity.　And　it　has　been　successfully　applied　to　the　AA　detection　in　the　real　samples　(urine)　with　satisfactory　results.　(C)　2011　Elsevier　B.V.　All　rights　reserved.