To study the influence of the resonant frequency in sound pressure transfer function on the frequency response characteristics of distributed feedback fiber laser hydrophone, a sensitivity enhanced structure through polyurethane end surface pulling is designed. The sound pressure transfer function model is established based on electro-acoustic theory. Then the relationship between the structure and material parameters with the sound pressure transfer function is simulated, and prototypes of hydrophones are fabricated and tested. The results show that the average sound pressure sensitivity reaches to -142.8 dB with the fluctuation less than ±1.5 dB in the frequency range of 10~2000 Hz and the resonant peak appears near 3150 Hz, which agrees well with the simulation result. The frequency response characteristics of fiber laser hydrophone can be effectively predicted,refined and optimized, which is of great guiding significance for the development of small array elements used in small-sized underwater combat platform.