In this paper, graphene sheets with different reduction levels have been produced through thermal reduction of graphene oxide in the temperature range of 200–900°C. The effects of interlayer spacing, oxygen content, BET specific surface area and disorder degree on their specific capacitance were explored systematically. The variation of oxygen-containing groups was shown to be a main factor influencing the EDL capacitor performances of the pyrolytic graphene. The highest capacitance of 260.5Fg−1 at a charge/discharge current density of 0.4Ag−1 was obtained for the sample thermally reduced at about 200°C.