Herein　the　electrochemiluminescent　behavior　of　a　promising　and　cheap　electrochemiluminescence　(ECL)　luminophore,　Eosin　yellowish　(2＇,4＇,5＇,7＇-tetrabromofluorescein,　EYH2),　was　investigated.　A　stable　and　strong　ECL　emission　of　Eosin　yellowish　could　be　achieved　at　electrochemical　pretreated　glassy　carbon　electrode　in　mild　acidic　media.　Based　on　proposed　stable　cathodic　ECL　of　Eosin　yellowish　on　the　electrochemically　pretreated　GCE,　some　important　bioactive　molecules,　such　as　H2O2,　guanine,　adenine,　nicotinamide　adenine　dinucleotide　(NADH),　uric　acid　and　vitamin　C,　were　found　as　enhanced　coreactants　towards　the　cathodic　ECL　of　Eosin　yellowish.