In this paper, a method for non-contact detecting the acoustic signal of tank gas leakage based on low-coherence optical fiber interferometer is presented. Vibration signals which caused by acoustic field of gas leakage are detected by low-coherence interference. The experimental results show that the vibration signals are wideband signals (0 Hz~90 KHz). While increasing the internal pressure, high-frequency components of the frequency spectrum have an obvious increasing trend, the amplitude and energy of the acoustic signal will both increase. The minimum detectable internal pressure of tank is 0.12MPa. The sensor is simple and reliable, and has a good practicability.