Vector hydrophones play an important role in underwater acoustic detection systems. In response to the low bandwidth problem of traditional piezoelectric ceramic based single-sided fixed cantilever beam structure hydrophones and the difficulty in miniaturization of compression type hydrophones, this paper proposes a double-sided fixed common mass block vector hydrophone based on the relaxation ferroelectric single crystal shear vibration mode. The vector hydrophone proposed in this article achieves higher receiving sensitivity due to the use of high-performance relaxor ferroelectric single crystals. The design structure using shear vibration mode is more conducive to miniaturization, and the double-sided fixed common mass block design is used to obtain higher working receiving frequency bandwidth. Simulation results show that the first-order resonant frequency of the double-sided fixed common mass block type vector hydrophone proposed in this article is 47 kHz, which is more than twice the first-order resonant frequency of the single-sided fixed vector hydrophone. The vector hydrophone proposed in this article is beneficial for the integration of underwater acoustic detection systems and the broadening of information sources.