Microbial electrochemical systems (MESs) suffer deterioration in power generation and wastewater treatment in practical application. In order to improve the performance of MESs when treating medium and high strength wastewater containing fermentative substrates, a continuous stirred microbial electrochemical reactor (CSMER) was developed by integrating MES and continuous stirred tank reactor (CSTR). Maximum power densities of (583±9), (562±7), (533±10) and (572±6) mW·m^-2 were obtained by each separate cell of CSMER under continuous feeding mode (HRT=12 h) at COD concentration of 6 000 mg·L^-1. COD removal and methane production rate of CSMER were (87.1±1.1)% and (1.48±0.15) L·L^-1·d^-1, which increased by 61.6% and 244.2% in comparison with those of a control CSTR. Pyrosequencing analysis showed that the dominant genera in CSMER_CMZ were Clostridium (10.0%), Acidaminococcus (11.7%) and Lactococcus (10.8%), which were fermentative bacteria. The microbial electrochemical zone (MEZ) was dominated by Geobacter (14.5%), which was the most predominant known exoelectrogen. Due to the relatively complicated bacterial communities, the CSMER possessed high abundance both in acetoclastic methanogens (52.2%) and hydrogenotrophic methanogens (47.1%). Syntrophic process occurred between anaerobic digestion in the CMZ and current generation in the MEZ contributed to its better performance.