ANSYS is used to simulate the detection process of pulsed thermography, and it simulates one steel sample with two depths and four kinds of defects under the excitation of planar heat flow. The temperature evolution and distribution of the detected surface of steel sample are calculated, the temperature decay curves corresponding to the defects areas are extracted to calculate the reflective coefficients of the interface between steel and defects, and the calculation results are compared with the experimental results of pulsed thermography. The possibility of identifying the subsurface defect characteristics by finite element (FE) modeling is studied, and it can be used as reference for pulsed thermography to be used for quantitatively detection.