The ruthenium oxide-carbon composite electrodes with different carbon contents were prepared by a colloid method and then they were annealed at 240 ℃. The morphologies and the microstructures of the AC/RuO2 composites were characterized by thermo-gravimetric analysis, SEM and XRD, and their electrochemical properties were also tested. Results show that the compositing of active carbon and ruthenium oxide is beneficial to obtaining of fine particles and does not affect the structure of ruthenium oxide. When the carbon content increases from 13.4% to 36.18wt% in the AC/Ruthenium oxide electrode, the capacitance decreases from 664 F/g to 526 F/g, the energy density drops from 103.27 Wh/kg to 75.18 Wh/kg, and the power density increases from 0.48 kW/kg to 0.64 kW/kg as well as the impedance decreases. In addition, the colloid method is practical and convenient