Artificial electroactive biofilms have been developed as potential alternative to natural biofilms because the fabrication of them is simple, rapid, standardized and controllable. However, the construction of artificial electroactive biofilms usually involves cell dry process or the use of binding agents, which inevitably decreases the viability of the entrapped cells. Herein, a fast and convenient bacterial immobilization method is proposed as an attempt to construct an artificial electroactive biofilm for microbial energy harvesting, in which bacteria are captured by magnetically active nitrogen-doped Fe3O4/reduced graphene oxide composite and bring onto the electrode by means of external magnetic field. The resulting artificial electroactive biofilm produces higher current than the natural electroactive biofilm in the bioelectrochemical systems. The improved performance of the biofilm captured by nitrogen-doped Fe3O4/reduced graphene oxide can be attributed to its high surface, high affinity for the attachment of Geobacter sulfurreducens, and efficient extracellular electron transfer between microbial biofilm and electrode. Moreover, because of the magnetic activity of the resulting electroactive biofilm, the current produced from the artificial electroactive biofilm is magnetically switchable. This study offers a new approach to rapidly fabricate an artificial electroactive biofilm and provides an opportunity for the fabrication of a magnetically controllable microbial bioelectrochemical system.