Graphite felt is used as the bromine electrode in H2/Br2 fuel cell, which is surface modified by acidic oxidation and thermal oxidation for improving cell performance. The structure, composition, electrochemical properties and performances of the modified electrodes are characterized with X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, electrochemistry impedance spectroscopy and single cell polarization curves. The maximum power densities are improved from the original 0.51 to 0.62 and 0.69 W cm−2 after acidic oxidized at 80 °C for 8 h and thermal oxidized at 500 °C for 5 h, respectively. The performance improvement may be attributed to the increase in oxygen-containing functional groups and surface area which could increase the electrochemical catalytic activity and thus decrease the charge transfer resistance. However, the ohmic resistance and charge transfer resistance increase after superabundant oxidation, which causes badly deteriorates in cell performance.