Electrochemically　active　bacteria　(EAB)　use　extracellular　electron　transfer　(EET)　to　exchange　electron　with　extracellular　acceptors.　Previous　studies　regarding　the　measurement　of　EAB　were　based　on　either　extracellular　reduction　or　oxidation.　In　this　work,　we　developed　a　simple　electrochemiluminescence　(ECL)　assay　for　the　identification　and　detection　of　EAB.　The　results　of　this　proposed　method　revealed　that　EET　of　EAB　influenced　the　content　of　dissolved　oxygen　and　the　formation　of　Ru(bpy)(3)(2+center　dot)　thus　leading　to　qualitative　changes　of　the　ECL　signal.　EAB　with　the　ability　of　extracellular　reduction　(such　as　Shewanella　oneidensis　MR　1)　gave　enhanced　signal　on　ECL　emission　while　those　displaying　the　ability　of　extracellular　oxidation　(i.e.,　Sulfobacillus　acidophilus)　showed　the　opposite　effect　on　ECL　emission,　but　non-EAB　(i.e.,　Escherichia　colt)　did　not.　These　changes　in　ECL　intensity　were　also　proportional　to　the　cell　density　that　could　be　quantitatively　detected　in　the　concentration　range　of　(1.1　+/-　1)　x　10(5)-212　+/-　2　CFU/mL　(i.e.　Shewanella　oneidensis　MR-1).　Moreover,　the　measurement　of　the　ability　of　EAB　using　this　approach　was　in　agreement　with　measurements　using　the　dissimilatory　Fe(III)　reduction　method.　Compared　to　previous　reports,　this　method　displayed　a　continual　and　steady　ECL　signal　that　allowed　accurate　measurements　of　EAB.　Most　important,　only　a　low　cell　density　was　needed　in　this　Ru(bpy)(3)(2+)　-　based　ECL　method,　which　is　beneficial　for　cell　detection.