The invention relates to a preparation method for an environment-friendly elastomer high-temperature pipeline heat-preserving material insusceptible to cracking, belonging to the field of preparationof heat-preserving materials. The heat-preserving material prepared by using the preparation method provided by the invention fully utilizes the advantages of high strength, high elasticity, abrasionresistance, high-temperature resistance and tear resistance of a polyurethane elastomer, so the disadvantages of easy corrosion and poor decorativeness due to insufficient toughness of a rigid external protective coating heat-preserving material are solved, and the problems like frequent cracking, drooping and detaching of the structure of a heat-preserving layer due to high environmental temperature and frequent vibration in pipeline operation in the process of long-term application of the heat-preserving materials like glass wool are overcome; meanwhile, the polyurethane elastomer synthesized by adopting a quasi-prepolymer process provided by the invention reduces generation of toxic free isocyanate, so more environmental friendliness is realized.