Abstract: Rock-block collapse has been a hot issue in the study of geological hazards for many years, and it is difficult to prevent because of its sudden disintegration, which is a serious threaten to human life and property safety. Rock-block collapse is caused by dynamic failure derived from system instability, so it can be more effective to apply vibration characteristic parameters in damage assessment and early warning. By using a laser Doppler vibrometer, the cohesion damage of control fissure was analyzed by natural vibration frequency in the paper. Based on the modified limit equilibrium model, the safety factor of the block with a deteriorating structural plane was calculated by the frequency, which decreased from 1.17 to 1.04, in accordance with the reality. The results show that the natural vibration frequency can effectively identify the unstable rock cumulative damage and provide objective data for reasonable determination of the cohesion. The laser Doppler vibrometer technology based on natural vibration frequency can satisfy cumulative damage evaluation of unstable rocks. It will play a significant role in engineering applications in the future.