Sonic IR imaging is one of the emerging NDT methods. The detectability of the cracks is based on its heating effect, which correlates with several excitation conditions, for example the excitation position. For the unclear effect of excitation position on crack heating, the finite element model and the experimental system was utilized to study the characteristic of crack heating under different excitation positions, and made an effective verification by using the equivalent force, equivalent velocity and equivalent heat flux. The research shows that when the excitation position is under the crack face, the crack heating will be restrained as a result of vibration synchronization for the two crack surfaces. However, as the excitation position moves both sides, the crack heating will rise first and fall later with a fluctuation, and bigger engagement force can lead it more severe. The study results clearly demonstrate the effect principle of excitation position on crack heating, which may further lay the theory basis to the optimization of test conditions in the sonic IR imaging.