Abstract: A frequency-tunable film bulk acoustic resonator and a preparation method therefor are provided. The resonator includes a substrate, an air gap, a sandwiched structure formed by electrodes and piezoelectric layers, and an electrode lead-out layer, wherein the substrate is connected to the sandwiched structure formed by the electrodes and the piezoelectric layers, and a connection face of the substrate and the sandwiched structure formed by the electrodes and the piezoelectric layers is recessed towards inside of the substrate to form the air gap; and the electrode lead-out layer is connected to the sandwiched structure formed by the electrodes and the piezoelectric layers. The sandwiched structure formed by the electrodes and the piezoelectric layers includes a bottom electrode, piezoelectric layers, intermediate electrodes, and a top electrode, wherein the electrodes and the piezoelectric layers are alternately arranged to form the sandwiched structure.