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-H　2O2　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,　H　2O2　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.　©　2005　Elsevier　B.V.　All　rights　reserved.