The invention relates to a carbon nanoparticle with a high specific surface area and a preparation method thereof. The method comprises the following steps: firstly, dispersing a hydrophobic initiator and a surfactant into water, injecting a reaction monomer 1 and an acrylonitrile monomer and reacting; and meanwhile, adding the surfactant into a reaction system, reacting and then acquiring compound latex A; treating the compound latex A and coating a protecting layer on the surface thereof, thereby acquiring compound latex B; and drying, pre-oxidizing and carbonizing the compound latex B, thereby acquiring the solid carbon nanoparticle with the high specific surface area. The method disclosed by the invention has the advantages of simpleness and high efficiency; the finally prepared carbon nanoparticle has excellent dispersity, high size control accuracy and high specific surface area; and the diameter of the carbon nanoparticle is within 50-100nm and the specific surface area is within 700-1500m<2>/g.