Characteristics of heat transfer and signal evolution in thermal nondestructive testing (TNDT) in aluminum adhesively-bonded structures were studied by computer simulation based on the finite element method (FEM). The TNDT mathematical model of bonded structures was constructed in cylindrical coordinates. The evolutions of TNDT informative parameters versus defect size and depth were simulated by using the FEM analysis software ANSYS. Some simple regression expressions were obtained for the relations between the informative parameters and the defect parameters. It is shown that, at a fixed defect depth, the four informative parameters including the maximum differential temperature, maximum contrast, differential temperature peak time and best observation time, are linearly proportional to defect radius respectively. However, if defect radius is fixed, the maximum differential temperature and maximum contrast become a non-linear function of defect depth, and the differential temperature peak time and best observation time are linearly proportional to defect depth. It is believed that the obtained results may be of help in developing an inspection strategy for aviation aluminum panels.