Carbon aerogel modified graphite felt is prepared as electrodes for vanadium redox flow batteries. Morphology and the nano-porous structure of the carbon-carbon composite electrode is characterized. Properties such as cyclic voltammetry, electrochemical impedance and battery performance of the carbon-carbon composite electrodes are investigated. The results show that the specific surface area of the modified graphite felt is dramatically increased from 1.13 m2 g−1 to 57.16 m2 g−1. The charge transfer resistance is reduced from 1.84 Ω to 0.21 Ω and the energy efficiency of the unit cell equipped with the modified electrodes is increased by 32.66% at a high current density of 160 mA cm−2.