The sensitivity of optical fiber ring laser distributed sensing system based on the mechanism of chaotic system’s sensitivity to initial conditions is low. Fiber interferometer distributed sensing system’s sensitivity is high. In this paper, a distributed sensing system with the structure of chaotic fiber ring laser (CFRL) embedding a Sagnac loop interferometer is proposed by combining the property of zero order interference of chaotic light and reciprocity of Sagnac interferometer. It can be used to improve the sensitivity of CFRL sensing system. According to the changes of temporal waveforms, frequency spectrums and autocorrelation functions out of the systems under the same disturbance, the sensitivities are compared between the improved system and the original CFRL system. Experimental results show that the sensitivity of the proposed system is higher than that of the CFRL system. In addition, the response properties of the system under the same amplitude and different frequencies of disturbance signals are measured. The results show that the system can detect the disturbances in the frequency range from 10 kHz to 300 kHz and the responses are flat. The detection abilities to weak signals with different amplitudes are compared. With the rising of disturbance signals amplitudes under the same frequency, the autocorrelation amplitudes of the interference signals increase. In conclusion, the proposed system improves the sensitive to weak disturbance signals with different amplitudes and frequencies. The frequency and amplitude of the disturbance signals can be obtained by the frequency spectrum and autocorrelation function of the waveform of the system.