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• A functional BPE-ECL platform based on biocathode reducing oxygen was constructed. • Electrochemically active bacteria were able to catalyze oxygen reduction at the cathode of BPE. • A low detection limit of 30 CFU (30 mL system) could be identified within 30 min. A functional bipolar electrode-electrochemiluminescence (BPE-ECL) platform based on biocathode reducing oxygen was constructed for detecting electrochemically active bacteria (EAB) in this paper. Firstly, thiolated trimethylated chitosan quaternary ammonium salt (TMC-SH) layer was assembled on the gold-plated cathode of BPE. TMC-SH contains quaternary ammonium salt branch chain, which can inhibit the growth of microorganisms on the surface or in the surrounding environment while absorbing bacteria. Then, the peristaltic pump was used to flow all of the samples through the cathode, and the EAB was electrostatically adsorbed on the electrode surface. Finally, applying a constant potential to the BPE, bacteria can catalyze electrochemical reduction of O 2 , and decrease the overpotential of O 2 reduction at the cathode, which in turn generates an ECL reporting intensity change at the anode. In this way, live and dead bacteria can be distinguished, and the influence of complex food substrates on detection can be greatly reduced. [ABSTRACT FROM AUTHOR]