An alternative method for fabricating graphite fiber brush (GFB) electrodes was proposed. Two series of GFB electrodes with different lengths (L) and loaded fiber masses (m) were fabricated. The effects of m/L on the biomass distribution, active biomass content, electrochemical behavior and MFC performance were investigated. For the electrodes with a similar m but different L, substrate supply within the interior of GFB electrodes improved with L, leading to higher biomass content and consequently the improved performance. However, a complex trend was found for the electrodes with different m and similar L, due to the opposing trends of substrate supply and actual functional area for electrochemically active bacteria with m. Furthermore, m-normalized biomass content and power density of the GFB electrodes increased with decreasing of m/L ratio due to the improved graphite fiber utilization until 0.014 g mm(-1), below which they remained constant since the utilization of graphite fibers plateaued. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.