[Objective] Hydrogen production and the exoelectrogen activity under complex substrate microbial electrolysis cell (MEC) are of great significance to its application in wastewater treatment. [Methods] The characteristics of exoelectrogens were investigated with the single-chamber MEC fed by the artificial dairy wastewater under different applied voltages in this study. [Results] The maximum current could reach up to 261 A/m3 and the volumetric H2 production rate reached to 0.048 m3 H2/m3 d with the applied voltage of 1.2 V, which was increased by 467% and 700% compared with the applied voltage of 0.4 V, respectively. The COD and protein removal could be achieved by 59% and 74%, respectively. The COD removal at 1.2 V was improved by 22.5% compared with that at 0.4 V. The PCR-DGGE community analysis demonstrated that Geobacter sp., one of well-know exeoelectrogens, existed in anode colonies as the dominant bacteria. There might be a synergies relationship between exoelectrogens and non-electrochemically active bacteria. [Conclusion] MEC can use dairy wastewater as fuel, achieve the purpose of efficient degradation and produce hydrogen gas at the same time, which provides research ideas for the practical application of MEC.