With the wide application of aluminum alloy components in various fields, its internal defects will lead to the existence that the product cannot be used properly and even causes great potential safety hazard, and therefore three-dimensional (3D) inversion of the component defects to judge the defect shape has become increasingly important. Using an aluminum alloy cylinder with the internal defect of a center hole as the research object, based on the probe perpendicular incident water immersion ultrasonic testing method, after the obtained time domain signal is transformed into frequency domain signal by Fourier transformation, and according to the signal frequency domain relationship between testing component defect position and the same location of the reference component, the frequency domain and time domain data of the scattering field amplitude by Born approximation method required for defect inversion are obtained, and the 3D inversion of internal defects is performed. The experimental results show that there exists some error between the inversion result and the actual defect, but the internal defects of the aluminum alloy component are still better inversed by the Born approximation method.