Some resonant peaks in the frequency response curve of fiber laser hydrophone appear at the resonant frequency of sound pressure transfer function, which makes the working frequency band narrow. A distributed feedback (DFB) fiber laser hydrophone is designed with a sensitivity enhanced mental diaphragm structure. A sound pressure transfer function model of the DFB fiber laser hydrophone is established based on electro-acoustic theory. The influence of structural parameters of hydrophone on sound pressure transfer function is simulated, and the structure of hydrophone is optimized. Prototypes of hydrophones are fabricated and tested experimentally. The experimental results show that the average sound pressure sensitivity of the DFB fiber laser hydrophone can reach to -135.99 dB with the fluctuation range within ±0.6 dB in the frequency range of 2.5-10 kHz, and the resonant peak appears near the frequency of 16 kHz. The experimental results agree well with the simulation results. The study is of great guiding significance for the development of DFB fiber laser hydrophone.