The invention discloses an insulator comprising: an insulating sleeve; an inner liner layer bonded to the inner surface of the insulating sleeve; and an insulating shed bonded to the outer surface of the insulating sleeve. The inner liner layer is made of an epoxy resin composite material comprising epoxy resin and a high-temperature-resistant corrosion-resistant filler filling the epoxy resin. In the present invention, the inner liner layer on the inner surface of the insulating sleeve is made of the epoxy resin composite material containing the high-temperature-resistant corrosion-resistant filler, thereby improving the high-temperature resistance, corrosion resistance and arc resistance of the insulator. In some embodiments of the present invention, the epoxy resin composite material has thermal conductivity greater than 0.3W/m.K and has an excellent thermally conductive property so that the heat dissipation performance of the insulator can be improved and the high-temperature-resistant performance of the insulator is further improved.