Abstract: Based on the finite element software ABAQUS, a layered model of concrete aggregates and an aggregate model based on the Monte Carlo method were established, and the influence of the heterogeneity of the concrete-filled steel tube on guided wave propagation was studied. A model of the concrete-filled steel tube with axial defects was established, and the relationship between the axial defect size and the defect echo was analyzed. It was found that the amplitude of the guided wave echo signal decreases with the increase of the aggregate area ratio, and the guided wave propagation speed increases linearly with the increase of the aggregate area ratio. When the cross-sectional damage rate is constant, as the length of the axial defect increases, the stationary segment amplitude of defect response increases first and then decreases.