A single electrode hydrophone based on A1N piezoelectric film is proposed. The piezoelectric characteristics of A1N are combined with MEMS micromachining technology. COMSOL was used to analyze and simulate the resonance characteristics of the device in the low frequency range of 20~100Hz. The optimized thickness of the piezoelectric film was 0.8~1.0 μm, and the diameter of the vibration membrane was 100 μm. The process flow of device preparation is given in this paper. ICP precise etching of A1N membrane can improve the yield, The actual samples were tested for their environmental adaptability under high hydrostatic pressure. The structure of a single hydrophone array is 40 by 40, The actual size is 7 x 7mm, which can be used to prepare a high-performance hydrophone integrated system.