This paper reports on theory modeling and experimental verification of a miniature resonator of bulk acoustic wave.An AlN sandwiched air cavity cantilever structure between a bottom electrode and a top electrode is fabricated by using the microelectronic and micromechanical technology.The resonator has the features of miniature,high Q and low cost.The resonant frequency of the fabricated resonator is 20 MHz,Q is about 800 and the electromechanical coupling coefficient is about 0.5%.