The invention discloses a capacitor film with metallocene line-shaped low-density polyethylene resin as a base body and a preparation method thereof. The capacitor film is prepared from the following raw materials in parts by weight: 45-55 parts of metallocene line-shaped low-density polyethylene resin, 30-35 parts of LDPE (low-density polyethylene), 10-15 parts of homo-polypropylene, 3-5 parts of epoxy flaxseed oil, 2-3 parts of polyving akohol, 1-2 parts of calmogastrin, 1-2 parts of polyisobutene, 8-12 parts of diatomite, 1-2 parts of ferrocene, 0.8-1.2 parts of poly-4-methyl-1-amylene, 0.1-0.3 parts of polytetrafluoroethene, 9-11 parts of blanc fix, 0.6-0.8 part of antioxygen 1010, 0.3-0.5 part of triethyl acetyl citrate, 0.5-0.7 parts of fumarat, 3-5 parts of calcium stearate, 1.5-2.5 parts of N-2(amino ethyl)-3-ammonia propyl trimethoxy silane, and 1.4-1.8 parts of modified tree ash. The metallocene line-shaped low-density polyethylene resin serving as a primary raw material; the low-density polyethylene resin serving an auxiliary raw material and a plurality of auxiliary material additives are blended, extruded and subjected to film blowing, shaping and cuting to prepare the capacitor film. The capacitor film is simple in preparation method; and the diatomite, the blanc fixe and the modified tree ash are added to the raw materials at the same time. Therefore, the barrier property and the gas tightness of the film are increased; and the capacitor film has good resistance to pressure and shock resistance, and has the characteristics of high heat sealing strength and good heat sealing property at the same time.