The invention provides a high-frequency acoustic wave resonator and a preparation method thereof. The high-frequency acoustic wave resonator comprises a high-acoustic-velocity support substrate, an insulating dielectric layer which is located on the upper surface of the high-sound-velocity supporting substrate, a piezoelectric film which is located on the upper surface of the insulating dielectriclayer, and an interdigital electrode which is located on the upper surface of the piezoelectric film. By arranging the high-sound-velocity supporting substrate below the piezoelectric film, the soundvelocity of target elastic waves excited and propagated in the piezoelectric film can be increased, propagation of the target elastic waves can be effectively restrained, and the resonant frequency of the high-frequency sound wave resonator is improved; the insulating dielectric layer is arranged between the piezoelectric film and the high-sound-velocity supporting substrate, the leakage of electric field energy in the piezoelectric film can be effectively reduced, and the electromechanical coupling coefficient of the high-frequency sound wave resonator can be enhanced; by selecting the appropriate insulating dielectric layer, temperature compensation can be carried out on the high-frequency acoustic wave resonator, temperature drift of the high-frequency acoustic wave resonator is reduced, and temperature stability of the high-frequency acoustic wave resonator is improved.