In this letter, a fiber Bragg grating (FBG) dynamic strain sensing system using a semiconductor optical amplifier (SOA)-fiber ring laser (FRL) and an arrayed waveguide grating (AWG) demodulator is proposed. Due to the characteristics of SOA, it can act as the gain medium as well as light source. The AWG module is used as the wavelength demodulator. It is shown that SOA-based FRL sensors can accurately respond to 1.5 με dynamic strain signal with high frequency up to 120 kHz and almost no distortion in the waveforms. Experimental results show that the system can be used for acoustic testing, such as underwater ultrasonic detection and external impact monitoring. In addition, the simultaneous dual-channel demodulated system is investigated in detail to verify the multiplexing. This dynamic strain sensing system can be widely utilized in structural health monitoring because of its high stability, low cost and good multiplexability.