To investigate the effect of magnesium ion on the bulk performance of microbial fuel cell anode microorganism, analytical methods such as electrochemical measurement and high-throughput sequencing were applied to determine the potential promotion of magnesium on anode potential, electrochemical activity and anode microbial community structure under different ion concentrations were evaluated. With the magnesium ion concentration increased from 0.5 (M1) to 2.0 (M2) and further to 5.0 mmol/L (M3), the anode potential of microbial fuel cell was declined from-0.443(M1) (CK, vs. Ag/AgCl) to-0.469(M2) to-0.477 V (M3), respectively, in comparison with that of-0.417 V in control test. Accordingly, power density was enhanced from 36.65 mW/m² (CK) to 40.19 mW/m² (M1), 44.21 mW/m² (M2) and 45.48 mW/m² (M3). Furthermore, electrochemical activity and electricigen biomass were increased notably, indicating magnesium could enhance the power output of microbial fuel cell and played an important role in extracellular electron transfer.