It is controversial to introduce oxygen into anode chamber as oxygen would decrease the CE (Coulombic efficiency) while it could also enhance the degradation of aromatics in microbial fuel cell (MFCs). Therefore, it is important to balance the pros and cons of oxygen in aromatics driven MFCs. A R-MO (micro-oxygen bioanode MFC) was designed to determine the effect of oxygen on electricity output and phenol degradation. The R-MO showed 6-fold higher phenol removal efficiency, 4-fold higher current generation than the R-AN (anaerobic bioanode MFC) at a cost of 26.9% decline in CE. The Zoogloea and Geobacter, which account for phenol degradation and current generation, respectively, were dominated in the R-MO bioanode biofilm. The biomass also showed great difference between R-MO and R-AN (114.3 +/- 14.1 vs. 2.2 +/- 0.5 nmol/g). Therefore, different microbial community, higher biomass as well as the different degradation pathway were suggested as reasons for the better performance in R-MO.