In order to improve the energy density and power density of supercapacitors, the main concepts of this study are to exploit advantages of three different materials: high energy density of ruthenium oxides (RuO2), high power density of mesoporous carbon CMK-3, and high conductivity of carbon nanotubes (CNTs) to form a composite electrode. The crystallization and dispersion of RuO2, the effects of RuO2 mass fraction, and CMK-3/CNTs on energy/power densities are discussed. Microstructures of all the specimens are characterized by scanning electron microscopy (SEM), inductively coupled plasma-mass spectrometry (ICP-MS), transmission electron microscopy (TEM), N2 adsorption/desorption isotherm and X-ray diffraction (XRD) measurements. Furthermore, the specific capacitance and the ideal density of energy and power are derived from cyclic voltammetry (CV) method. In short, the combination of RuO2, CNT, and CMK-3 lead to enhanced the specific capacitance of 1102F/g, energy density of 0.15Wh/g and power density of 237W/g, which are 4 times and 3 times greater than those of CMK-3, respectively. The results provide effective routes to enhance the capacitance.