Ruthenium oxide particles were supported on graphene sheets (GS) by hydrothermal and low temperature annealing process. The GS was prepared from graphene oxide by an expansion process and different expanding temperatures were studied and polystyrene sulfonate sodium was used as dispersion agent of hydrophobic GS. Different Ru content of the RuO2/GS composites on the influence of the electrochemical properties was studied. Atomic force microscope analysis was applied to test the layers of GS. The morphology of GS and RuO2/GS composites were confirmed by field emission transmission electron microscopy analysis. X-ray diffraction, Raman spectroscopy and liquid-nitrogen cryosorption were used to characterize the structure and morphology of the GS and RuO2/GS. The RuO2/GS (Ru:40 wt%) composites used as electrode materials of supercapacitors exhibited a specific capacitance of 551 F/g at 1 A/g in 1 M H2SO4 electrolyte. Besides, both the rate capability and cycle performance of RuO2/GS composites had a great improvement compared with GS. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.