The invention belongs to the technical field of sealing parts in automobile engines, transmissions, steering systems and fuel oil injection systems and particularly relates to a preparation method of a high-temperature-resistant sealing part for automobiles. The method includes multi-step plasticating, molded part forming and sealing part forming. Compared with the prior art, the preparation method has advantages that by synergistic effects of hydroxyl carboxyl hybrid polyester, industrial hemp core powder, aluminum tristearate, metallocene polyethylene and polyamide resin, creep relaxation and tensile strength are achieved, high dimensional stability in high-temperature operation is realized, an effective sealing effect can be achieved, and influences on use due to proneness of expansion of the sealing part under a high-temperature condition are effectively avoided; the preparation method is simple and suitable for large-scale production and popularization.