In a typical microbial electrochemical system (MES) with dual-chamber for Cr(VI) reduction, it was faced with the decline of Cr(VI) reduction efficiency after several cycles of operation, which limited the continuous and effective Cr(VI) reduction of MES. In this study, a novel bioelectrochemical reactor assembled with cooperative cathodes of chemical cathode and bio-cathode (BERCC) and with excess sludge as anodic substrate was designed to solve the problem. Comparative study of BERCC and BER with dual chemical cathodes (BERDC) revealed that BERCC broke through the limitation of Cr(VI) reduction decline for cycles of operation and improved performance of electricity generation. Both the Cr(VI) reduction rate and the power density were increased with the decrease of pH and the increase of TCOD and initial Cr(VI) concentration. Cooperative cathodes stimulated the growth of electrochemically active microorganisms in the anodic biofilm and produced 8.21±0.64 mg Coulomb/(L·h) more electrons than dual chemical cathodes, which enhanced the electrons for electricity generation and Cr(VI) reduction by about 58.3% and 56.1±5.6% in BERCC than those in BERDC.