The transient heat conduction of TBC(thermal barrier coatings) structures in TNDT(thermal non-destructive testings) was described by an axisymmetrical model in a cylindrical coordinate, and the corresponding physical model was constructed. The temperature field of TBC structures stimulated by a heating pulse was analyzed by using the FEA(finite element analysis) software ANSYS, and the relations between information parameters(such as maximum differential temperature and maximum contrast) and defect parameters(such as defect radius, depth, coating thickness and thickness difference) were studied. The results show that, at a fixed coating thickness, the maximum differential temperature and maximum contrast are a nonlinear function of the defect radius respectively and increase with the defect radius, and their saturation value exist. At a fixed defect radius, the maximum differential temperature and maximum contrast are a nonlinear function of the coating thickness respectively, and decrease when the coating thickness increasing. These results provide a theoretical support for the detection and characterization of delamination in TBC structures by infrared thermography.