The invention provides a current transformer insulation material and a preparation method thereof, and relates to the technical field of current transformer processing. The insulation material is prepared from, by weight, 25-30 parts of methyl silicone rubber, 18-20 parts of ethylene-propylene-diene monomer rubber, 10-12 parts of an epoxy resin, 3-4 parts of strontium titanate nanoparticles, 4-6 parts of methyl tin mercaptide, 2-4 parts of calcined clay, 1-3 parts of paraffinic hydrocarbon oil, 2-3 parts of 1,2-bis(2,3,4,5,6-pentabromophenyl)ethane, 2-4 parts of methyl ethyl ketone peroxide, 1-3 parts of dodecanedioic acid, 0.4-0.6 part of 2-butoxyethyl acetate, 1-1.2 parts of carbon fibers, 0.8-1 part of basalt fiber, 0.8-1 part of 1,2,3-triazole, 1-3 parts of an antioxidant, 1-1.6 partsof a plasticizer and 0.8-1.4 parts of a coupling agent. The preparation method of the invention overcomes the deficiencies of the prior art, improves the dielectric strength and the aging resistance of traditional current transformer insulation materials, effectively improves the service life of the product, and is suitable for promotion and production.