The invention discloses a novel insulated sealing material for an insulated joint and a preparation method of the novel insulated sealing material. The sealing material is prepared from the following components in a mass ratio: 99 to 100 of fluororubber, 3.5 to 4.5 of MgO, 5.5 to 6 percent of CaO, 17 to 17.5 of calcium fluoride, 17 to 17.5 of calcium carbonate, 0.45 to 0.5 percent of No.3 vulcanizing agent, 2.3 to 2.5 percent of dual powder AF and 0.35 to 0.4 percent of benzyl triphenyl phosphoric chloride serving as a vulcanizing assistant. The novel insulated sealing material disclosed by the invention has the beneficial effects that by adjusting a formula and a production process of the fluororubber, breakdown voltage of a fluororubber material is improved; meanwhile, indexes such as hardness, mechanical properties, corrosion resistance and insulation resistance of the material are guaranteed, so as to meet the requirements of the insulated joint.