The fiber hydrophone utilizes the interferential optical signal to detect. The effect of the stimulated Brillouin scattering (SBS) occurs with the increase of the optical power, which makes noise, limits the incident light power and affects the detecting signal seriously. For suppressing the SBS to improve the characteristic of fiber hydrophones, research, based on the Michelson fiber hydrophone, was done, and the methods of increasing the threshold, especially the method of using the optical isolator were investigated according to the threshold equation. The time-space distribution of incident light, Stokes light and sound wave in the fiber is analyzed with FDTD. The time-space distribution of each wave in the fiber can be obtained so long as the initial condition and fiber parameters are given. The research on suppressing this effecting can offer a new way to produce the tunable coherent light, and it can be an effective method to study the characteristic of different scatterings in fiber system.