The invention belongs to the field of electric materials, and discloses an insulating material for a transmission line. The insulating material for the transmission line is prepared from, by weight, 1-2 parts of magnesium oxide, 1-2 parts of antimonous oxide, 1-2 parts of oleamide, 1-2 parts of borax, 2-3 parts of triphenyl phosphate, 2-3 parts of zinc borate, 2-3 parts of glass fiber, 3-4 parts of palygorskite, 4-6 parts of stearic acid, 5-7 parts of egg shells, 5-7 parts of kaolin, 8-10 parts of aluminum nitride, 8-10 parts of triallyl cyanurate, 12-15 parts of chlorinated polyethylene, 16-20 parts of ethylene propylene diene monomer and 16-20 parts of hydrogenated acrylonitrile butadiene rubber. The insulating material for the transmission line is good in insulating property and flame retardant property, excellent in mechanical property, good in corrosion resistance and suitable for various environments, the application range is greatly widened, and the service life is greatly prolonged.