The invention belongs to the field of power cables and particularly relates to an anti-corrosion flame-retardant wind power cable sheath, an insulating material and a preparation method of the sheath and the insulating material. The inner layer insulating material is prepared from, by weight, 40-60 parts of EPDM, 10-25 parts of polyvinyl chloride, 5-10 parts of paraffin oil, 5-15 parts of calcium carbonate, 30-60 parts of kaoline, 1-3 parts of anti-ageing agent, 1-3 parts of assistant crosslinker, 0.5-2 parts of vulcanizing agent and 1.5-3.5 parts of flame-retardant agent. The outer layer sheath material is prepared from, by weight, 40-60 parts of ethylene propylene terpolymer A, 35-60 parts of ethylene propylene terpolymer B, 3-8 parts of activating agent, 2-4 parts of stabilizer, 2-4 parts of antioxidant, 2-4 parts of cold-resistant plasticizer, 1-3 parts of silane coupling agent, 5-10 parts of compound vulcanizing agent, 3-8 parts of flame-retardant agent and 30-50 parts of filling agent. Process improvement is conducted on the inner layer insulting material and the outer layer sheath material of a wind power cable, the cable can be used in the environment of -40-100 DEG C for a long time, the cable has good softness, oil resistance, cold resistance, abrasion resistance, acid and alkali resistance, flame retardancy and the like, and the requirement that a draught fan safely and normally runs in the changeable and severe weather environment is met.