Abstract: The biocompatibility and dispersity of graphene are deteriorated due to its hydrophobicity and - conjugated effect which make it difficult to modify carbon-based electrodes. This problem was solved by mixing graphene with carbon nano-tube through non covalent binding in this study and the composite graphene-carbon nano-tube modified electrode was prepared by the dip method. Observation by the scanning electron microscope clearly indicated that the surface of the carbon felt electrode was covered by the homogeneous layer of graphene-carbon nano-tube. The electricity generation performance of the microbial fuel cell (MFC) was greatly improved by the composite graphene -carbon nano-tube modified anode. The MFC with the modified anode produced a maximum power density of 7607 mW/m2 which was 236-fold higher than that produced by the MFC with a bare carbon felt anode (2288 mW/m2). The electron transfer impedance of the anode was significantly decreased by the composite graphene-carbon nano-tube, with 398 for the modified anode and 2487 for the bare anode, which could explain the performance improvement of MFC.