Abstract: Under cyclic dynamic loading, cracks in reinforced concrete (RC) structures experience repeated opening, closing, sliding, and contact, resulting in pronounced crack-surface effects that significantly affect the propagation paths and attenuation characteristics of stress waves. However, the effects of crack-surface affect behavior under varying axial compression ratios on stress wave propagation and the corresponding smart aggregate (SA)-based monitoring signal responses remain unclear. To address this issue, three RC columns were embedded with the SAs in the plastic hinge region and tested under low-cycle reversed loading with axial compression ratios ranging from 0.1 to 0.3. Stress-wave monitoring signals corresponding to the full evolution of cracks—from initiation to propagation—were collected, and the influence of crack-surface effects on stress-wave attenuation was investigated using a wavelet packet energy analysis method. The results show that as the axial compression ratio increases, crack patterns evolve from predominantly horizontal cracks to a combination of diagonal and vertical cracks, accompanied by an increase in both the crushed concrete area and the height of the plastic hinge region. Monitoring signals with higher initial energy exhibit faster attenuation. The energy of corner SAs decays rapidly when the drift ratio is below 1.14% and then stabilizes, whereas the energy of mid-region SAs changes slowly for drift ratios less than 0.57%, drops sharply between 0.57% and 1.14%, and subsequently remains at a low level. Overall, the SAs can effectively monitor the crack surface effect in RC columns under combined axial load and bending.