Amorphous nanostructured composite materials with different RuO2 loadings on carbon were prepared by colloidal method. The annealing temperature was found to be critical in optimizing the electrochemical performance of this material. FT Raman study confirmed that ruthenium complex converted to ruthenium oxide after annealing at 100°C. The specific capacitance of RuO2/carbon composite electrode (40wt.% Ru) was calculated by using cyclic voltammetry, which was to be 407F/g. The specific capacitance of RuO2·xH2O was estimated to be approximately 863F/g by subtracting the contribution of double layer capacitance resulting from carbon in the composite. Transmission electron microscopy indicated that the particle size of RuO2·xH2O on carbon was approximately 3nm. By increasing the Ru loading over 60wt.%, the particle size of RuO2 increased up to several micrometers resulting in a decrease of the utilization of RuO2, the specific surface area and the rate capability.