Two chamber microbial fuel cells (MFC) were constructed and inoculated with Geobacter sulfurreducens. The exoelctrogen suspension was dynamically treated in 0, 100, 200 mT vertical magnetic fields for 1 h respectively and then inoculated into MFC1, MFC2 and MFC3 to study the effects of dynamic magnetic field on electricity production. The results showed that treatment with dynamic magnetic field prelonged the startup time, lowered the steady voltage, and increased the apparent internal resistance of reactors. The apparent internal resistance of MFC1, MFC2 and MFC3 were 329, 507 Ω and 353 Ω respectively. The test results of electrochemical impedance spectroscopy indicated that the MFC with magnetic treatment had the higher charge transfer resistance compared to those without magnetic treatment. The charge transfer resistance of MFC1, MFC2 and MFC3 were 12.34, 28.29 Ω and 16.87 Ω respectively. The measurement of cyclic voltammetry found that the treatment with dynamic magnetic field reduced the electrochemical activity of exoelctrogens.