The invention discloses a novel high-hardness plastic shell composition for a capacitor. The novel high-hardness plastic shell composition is characterized by consisting of the following components in parts by weight: 35 parts of polypropylene, 15 parts of linear polyethylene, 10 parts of a high barrier film, 5 parts of polypropylene random copolymer, 5 parts of di-tert-butyl peroxide, 2 parts of cassava flour, 5 parts of modified wood plastic powder, 2 parts of tributyl citrate, 2 parts of silicone rubber, 2 parts of glycerol, 5 parts of carbon fiber, 2 parts of a rear-earth light converter, 2 parts of diphenyl silanediol, 2 parts of a plasticizer, 2 parts of silicon carbide micro powder, 2 parts of a lubricant, 2 parts of paraffin, 2 parts of vermiculite, 2 parts of sepiolite fabric, 2 parts of glass fibers, 2 parts of rear earth and 2 parts of talcum powder. The novel high-hardness plastic shell composition disclosed by the invention is simple in component and low in cost; the prepared finished product has good toughness, strong bearing capacity and high compactness, is easy to degrade and nonhazardous under a high temperature environment; meanwhile, the conventional preparation process is changed and a freezing process is increased, so that the safety of the product is improved and the product has relatively good stable performance at a relatively high temperature.