The characteristics of the fiber-optical hydrophone systems based on the all optical fiber Mach-Zehnder′s interferometer were tested and analyzed,according to optical fiber hydrophone working principle.The experimental system was built and the performances of fiber-optic hydrophone were tested in different conditions.The result shows that with the increasing of sphere of fish activities and the decreasing of surrounding temperature,the detection sensitivity is linear decline and the least resolution is decreased,which are corresponded with the calculated ones.