In order to reduce the complexity of the traditional distributed acoustic sensor（DAS） system and improve the signal-to-noise ratio（SNR）, a DAS system based on a fiber ring laser（SOA-FRL） based on a semiconductor optical amplifier is proposed. This system uses SOA-FRL to replace the narrow linewidth laser and pulse modulator in the traditional DAS system, and realizes the highly stable optical pulse output. The double pulse heterodyne detection method is used to achieve accurate sound signal detection and sound source location. The experimental results show that the demodulation SNR of the proposed system is as high as 38.25 dB and the spatial resolution is 12 m under the action of the acoustic signal with frequency of 1 kHz and amplitude of 1.14 rad.