The invention discloses a stretch-proof cable sheath insulation material and a preparation method thereof. The stretch-proof cable sheath insulation material comprises the following raw materials in parts by weight: 97-103 parts of neoprene CR121, 13-17 parts of SG-4 type PVC (Polyvinyl chloride) resin, 14-22 parts of semi-reinforcing carbon black N774, 2-3 parts of magnesium oxide, 1-2 parts of aluminic acid ester coupling agent, 30-33 parts of blanc fixe, 1-2 parts of antiager MB, 1-2 parts of 2-thiol group benzimidazole, 5-7 parts of polyamine wax micro powder, 1-2 parts of promoter DM1, 0.8-1 part of promoter TMTD, 14-18 parts of high wear resistance carbon black N330, 1.-1.2 parts of adipic acid propylene glycol polyester, 2-4 parts of zinc borate, 4-6 parts of glass powder, 0-8-1 part of zinc oxide, 2-3 parts of modified bentonite, 4-6 parts of ethylene thiourea, 2-3 parts of ammonium dihydrogen phosphate and 0.8-1 part of N-2-(amino ethyl group)-3-aminopropyl trimethoxy silane. The stretch-proof cable sheath insulation material prepared by the method has the advantages of excellent physical properties, stable size, low percentage of contraction and greatly increases tensile strength, tearing strength and resilience force performance and has the performances of common silicon rubber at the normal temperature and forms a hard shell after ablated in high-temperature fire to protect a burned objected from being damaged.