The invention provides an insulator and a preparation method, wherein the insulator comprises an insulator main body and a protective layer covering the surface of the insulator main body; the protective layer is made from fluorine silica gel, a fumed silica and ablation-resistant composite material, wherein the content of the fluorine silica gel is 30-80wt% of the total mass of raw materials. The fumed silica and ablation-resistant composite material has the properties of being resistant to a high temperature, high in heat resistance, high in insulation and good in fluorine silica gel affinity, can be used for storing heat or performing heat conversion, so that the insulator has a good heat insulation function, the probability that the insulator is exploded is reduced, and the probability that the guide wire mounted on the insulator is dropped is reduced.