The invention provides a cavity type bulk acoustic wave resonator without preparing a sacrificial layer and a preparation method of the cavity type bulk acoustic wave resonator. The method comprises the following steps that a piezoelectric single crystal wafer which is subjected to ion implantation and provided with a bottom electrode is taken, a cavity is formed in the side, provided with the bottom electrode, of the piezoelectric single crystal wafer, then a substrate is taken, and the substrate and the side, provided with the cavity, of the piezoelectric single crystal wafer are bonded; andheat treatment is carried out on the bonded intermediate product to strip the film of the piezoelectric single crystal wafer, and then a top electrode is produced on one stripped side of the piezoelectric single crystal wafer to obtain the cavity type bulk acoustic wave resonator. According to the preparation method of the cavity type bulk acoustic resonator without the need of preparing the sacrificial layer, the sacrificial layer does not need to be grown, etching and trepanning are not carried out on the thin film, the mechanical strength of the device is improved, and damage to the thin film is not likely to be generated; the cavity structure is formed before film formation, the rate of finished products is high, residues left by etching after film formation do not exist, and the influence of incomplete release on the device does not need to be considered.