A distributed optical fiber acoustic sensing system based on chaotic laser interference is proposed, which uses the external cavity feedback semiconductor chaotic laser as the sensing light source, and the non-equal length of Mach-Zehnder arms for the introduction of the interference optical path difference. The reciprocal effect of the annular interference system is overcome by the linear Sagnac structure. The spectral null-frequency point is applied to realize the distributed location of sound signals.The experimental results show that, this system can real-time extract the single-tone signal with a frequency of 1 kHz and the voice signal in the frequency range of 200-900 Hz. Compared with the traditional broadband amplified spontaneous emission laser, this acoustic sensing system based on chaotic laser interference has a better sound frequency response curve, a higher detection sensitivity and a uniform plane directivity. Moreover, a broad-spectrum sound positioning in a 12 km single-mode fiber is achieved, which provides a new sensitivity enhancement solution for the distributed optical fiber acoustic sensing system.