 Terahertz time-of-flight tomography (THz-TOF) and THz optical coherence tomography (Thz-OCT) are mainly used in implementation.In diffraction tomography, the detection beam interacts with the target and uses the resulting scattered waves to build a 3D image of the sample.The diffraction effect and the diffraction slice theorem shine light on the surface of the scattered object and record the reflected signal to obtain the diffraction field distribution after the sample in order to explore the surface shape of the target object.