Cobalt Alumino Silicate Ceramic (CASC) composites, with different molar weight concentration (i.e. G₀=0, G₁=0.4, G₂=0.6, G₃=0.8, G₄=1.0, and G₅=1.2 (M.W.)) of cobaltus acetate are prepared via sol-gel route. XRD shows mullite and cobalt aluminate phase which is found to depend on the concentrations of Co⁺² ions. Field emission scanning electron microscope (FESEM) images show for all samples of CASC nanocomposites after sintering at 1400^oC, nano sized cobalt aluminate grains are embedded in evenly spread mullite grains; but in case of G₀, there are only evenly spread mullite grains. The study of dielectric property of the composite samples at room temperature shows that at all concentration (G_1, G₂, G₃, G₄ and G₅) the dielectric constant is higher than pure mullite (G₀) and there is a critical concentration of cobaltus acetate (G₃) where there is maximum enhancement of dielectric constant in the higher frequency range from 40 KHz to 2 MHz. The dielectric constant varies from 44.77 to 37.75 for G₃ and from 29.8 to 24.12 for G₀ respectively. The tangent loss of composite with G₃ has the lowest value than that of other concentrations including pure mullite in the frequency range 40 KHz to 2MHz. Due to high dielectric constant and low tangent loss, the composite with specific concentration and in the high frequency range has great importance as an electronic material.