Bioelectrochemical systems (BES) is a promising strategy for azo dyes decolorization enhancement in carbon-limited condition, but decolorization products need further aerobic mineralization. Here, a counter-diffusion biofilm-supported BES (E-MABR) was designed to achieve the decolorization, mineralization and denitrogenation of Alizarin Yellow R (AYR) in electron-deficient wastewater. The introduction of electrodes facilitated the secretion of extracellular polymeric substances (EPS), particularly proteins (PN), whose content in the cathodic biofilm was 2.5 ± 0.2 times higher than that in the MABR. Additionally, electrical stimulation enriched electroactivity bacteria (e.g. Geobacter) and azo dyes metabolism contributor (e.g., Thauera and Dechloromonas), and significantly upregulated the expression of decolorization-related genes, particularly azoR (1.2 log