The　detection　of　proteins　is　very　important　in　the　study　of　biochemistry　procedure,　and　electrochemiluminescence　method　is　a　very　practical　tool　for　the　study　of　protein　folding,　structure　and　quantification.　In　this　work,　bovine　serum　albumin　(BSA)　and　casein　were　found　to　be　able　to　significantly　quench　the　electrochemiluminescence　(ECL)　of　Ru(bpy)32+/TPrA　system,　based　on　which　a　highly　sensitive　approach　for　the　detection　of　protein　was　proposed.　Under　the　optimized　conditions,　the　logarithmic　plot　of　the　inhibited　ECL　versus　the　concentration　of　BSA　and　casein　were　linear　over　the　ranges　of　1-30　μg/L　and　0.1-1.6　μg/L,　respectively.　The　corresponding　limit　of　detection　(LOD)　was　0.45　μg/L　for　BSA　and　0.026　μg/L　for　casein　(S/N　=　3).　UV,　ECL　and　fluorescence　methods　were　used　to　investigate　the　mechanism　of　the　inhibited　ECL　of　Ru(bpy)32+/TPrA/BSA　system.　A　mechanism　based　on　the　formation　of　protein-Ru(bpy)32+　super　molecule　was　proposed,　which　would　prevent　Ru(bpy)32+　from　reaching　the　working　electrode　surface　so　that　induced　ECL　quenching.　©　2011　Elsevier　Ltd.　All　rights　reserved.