The chaos generated by the external-cavity feedback semiconductor laser has an obvious relaxation oscillation and the energy of the low-frequency band is low, limiting the dynamic range of chaos optical time domain reflectometry (OTDR). An optical fiber ring structure is proposed herein to improve the dynamic range of the chaos OTDR. Experiments and numerical simulation find that multibeam interference occurs when the chaotic light passes through the fiber ring. Moreover, the energy of the low-frequency band is improved by delaying the self-beat frequency effect. The experimental detection results show that the dynamic range of the chaos OTDR increases by 5 dB when the fiber ring is used under a 200-MHz detection bandwidth.