Abstract: For the nondestructive testing of the laser scanning infrared thermography, description is focused on its theory, detection principle, and the temperature-time dependence. A 2-D heat transfer model was established. The surface temperature distribution for infinite thick sample was calculated by using Fourier transform, and temperature field distribution for finite thick sample was obtained by using the method of mirror imaging. Based on this theory, it is concluded that depending on the thermal conductivity of the sample, for certain range of the laser scanning speed, the surface temperature variation is the same as the 1-D heat transfer model. This establishes the theoretical foundation for the laser scanning infrared thermography.