Abstract: In order to detect the damage of simple-supported reinforced concrete (RC) beams, experiment set-up for RC beams dynamic test was designed. In the test, the beam was subjected to an increasing static load in the middle to introduce cracks, and the last load step corresponded to failure. After each load step and unloading, the beam crack width was investigated and an experimental dynamic monitoring was performed. The multipie degree-of-freedom dynamic equation of the testing beam was wavelet transformed, and the structural dynamic response expression on multi-scale was acquired. It is shown that multi-scale decomposition of signal comprises more structural damage information. By means of DASP signal processing system, binary wavelet transformation is applied to the dynamic signal of reinforced concrete beams on different damage states. Through analyzing the wave-figure of all frequency scales, the damage of reinforced concrete beams is determined.