Abstract: Since the emergence of concrete-filled steel tubes (CFSTs) structures, defect detection has been an important research topic. In recent years, CFSTs structures have been increasingly used in larger diameters and longer spans. However, existing detection technologies are insufficient to meet the requirements for large-diameter and long-distance CFSTs structures. The impact elastic wave is a kind of stress wave with large excitation energy, long propagation distance, and convenience for spectral analysis, which can solve the technical difficulties encountered by the existing defect detection technologies for CFSTs. To study the effectiveness of the impact elastic wave technique in defect detection of CFSTs, this study investigates defect detection in CFSTs from three aspects: theoretical analysis, finite element simulation, and practical application. Theoretical research reveals that when there are defects inside CFSTs, the propagation velocity difference of elastic waves between concrete and air is significant. Moreover, elastic waves follow the principle of minimal propagation path length when propagating in CFSTs, causing the impact elastic waves to bypass defective regions during propagation. Therefore, impact elastic wave detection is feasible for identifying defects in CFSTs, and the distribution of wave velocity within the cross-section can serve as a key indicator for evaluating defect presence. The finite element software COMSOL was used for simulation to verify the effectiveness of the theoretical research by simulating the propagation path and wave velocity distribution of impact elastic waves. Finally, in practical engineering applications, the impact elastic wave nondestructive testing technology was employed. By analyzing the wave velocity distribution in CFSTs, the preset defects were successfully identified, demonstrating high detection accuracy and reliability.