The　main　aim　of　this　paper　is　to　explore　a　new　label　for　electrochemiluminescence　(ECL)　bioassays.　Tetra-substituted　sulphonated　cobalt(II)　(CoTSPc)　acting　as　a　mimetic　peroxidase　of　horseradish　peroxidase　was　first　found　to　be　able　to　catalyze　the　ECL　reaction　of　luminol-H2O2　at　a　glass　carbon　electrode.　CoTSPc　also　retained　its　ECL　catalytic　activity　when　it　was　conjugated　to　BSA.　Moreover,　the　enhanced　ECL　intensity　of　the　luminol-H2O2　system　at　pH　7.4　was　proportional　to　the　amount　of　target　bovine　serum　albumin　(BSA).　The　spectrum　characteristics　of　CoTSPc-BSA　conjugate　was　examined.　The　effects　of　the　pH,　reaction　medium　of　the　solution,　the　concentration　of　luminal,　H2O2　and　the　electrochemical　scanning　mode.　were　also　investigated.　Although　refinements　in　the　technique　are　still　necessary　before　it　can　be　used　in　practice,　a　new　ECL　probe　for　protein,　CoTSPc,　has　been　preliminarily　developed.　(c)　2005　Elsevier　B.V.　All　rights　reserved.