The invention relates to a carbon aerogel. The specific surface area of the carbon aerogel is 700-820m<2>/g, the aperture distribution is 5.94-12.22nm, the pore volume is 0.6-1.1cm<3>/g, and the specific capacitance is 94-125F. The invention also relates to a preparation method of the carbon aerogel. The preparation method comprises the steps of (1) organic wet gel preparation, (2) solvent displacement, (3) normal pressure drying, and (4) high temperature charring. Organic wet gel is prepared from resorcinol or a resorcinol and m-trihydroxybenzene mixture and formaldehyde by adding ascorbic acid through a sol-gel technology; the ascorbic acid (VC) is introduced to raw materials to prepare VC-carbon aerogel, and the VC belongs to lactone and can release micro-molecular gases with the change of the pH value of a reaction solution in the reaction process in order to greatly affect the specific surface, the aperture and the pore volume in the gel generation process, so the reaction speed is improved, the specific surface area is increased, the aperture and the pore volume are increased, and the conductive performance is enhanced.