Cobalt-based composite aerogel was synthesized by sol-gel process and CO2 supercritical drying. The morphology of aerogel was evaluated by field-emmision scanning electron microscope (FESEM) and high-resolution transmission electron microscopy (HRTEM), which suggest that the aerogel was made up of 3-D networks and the skeletal was composed of cobalt oxide colloidal particles with amorphous carbon. The N2 adsorption/desorption shows that the aerogel has high BET surface area of 177 m?g, average pore diameter about 4nm, which means the aerogel possesses the typical characteristic of mesopore. Then cobalt-based composite aerogel was annealed, and the crystal structure of Co3O4 aerogel was investigated by the XRD patterns, The N2 adsorption/desorption showed the aerogel with surface area about 54m2/g and the distribution of pore-diameter around 7nm.