Phenazines are a kind of metabolites that can mediate extracellular Pseudomonas aeruginosa (P. aeruginosa) cells in microbial fuel cells (MFCs). However, it is still not clear that whether and how the excretion profile of phenazines is affected by the operating MFC. Here, we report a real time analysis approach based on a cavity microelectrode electrochemical sensor to investigate the phenazines excretion behavior of P. aeruginosa during MFC operation. The phenazine concentration increases at first 72 h, reaches a plateau and decreases after 120 h and also shows local dependent variation. It is dependent on the MFC current generation profile but also affect by the biofilm formation. Accordingly, a mechanism about phenazines excretion in MFC anode and the phenazines mediated extracellular electron transfer of the P. aeruginosa anode is proposed. This work provides a novel strategy for self-mediated extracellular electron transfer analysis in the operating MFCs. (C) 2015 Elsevier Ltd. All rights reserved.