The invention discloses an ageing resistant power line sheath material and a preparation method thereof. The ageing resistant power line sheath material is prepared by using the following raw materials, by weight, 45-65 parts of ultrahigh molecular weight polyethylene, 25-35 parts of chloroprene rubber, 10-20 parts of polybutylene terephthalate, 1.5-2.5 parts of vinyltrimethoxy silane, 2-3 parts of dicumyl peroxide, 4-8 parts of basic magnesium carbonate, 22-28 parts of nanometer kaolin, 14-26 parts of glass bead, 3-6 parts of glyceryl monoricinoleate, 10-15 parts of nylon acid dibutyl ester, 8-16 parts of dicyclohexyl phthalate, 5-10 parts of phosphoric trichloride, polymer with 1,3-benzenediol, phenyl ester, 5-10 parts of tris(2,3-dibromopropyl)isocyanurate, 1-2 parts of dibasic lead phosphite, 1-2 parts of calcium stearate, 1-2 parts of barium stearate, 4-6 parts of paraffin oil, 0.5-1.5 parts of tetramethylthiuranm monosulide, 1-2 parts of 2-mercaptobenzothiazole and 20-25 part of an assistant. The sheath material has the characteristics of strong ageing resistance, good chemical stability, high mechanical strength, wide use temperature, excellent flame resistance, excellent impact resistance, excellent wear resistance, excellent chemical corrosion resistance, durability, and wide application prospect.