Abstract: Eddy current thermography has been applied to detect surface and near surface cracks of metal parts, which have high detection efficiency and capability of large one-time detection area. The heat conduction and resistivity of material can be changed by impact fatigue damage due to the change of microstructure and stress distribution of the material caused by impact fatigue damage. In this paper, eddy current thermography is employed to detect impact fatigue damage of metallic material. A detection system is established. The thermal image sequences of aircraft brake block have been captured with eddy current thermography. The images have been analyzed according to the principle of the change of thermal conductivity and resistivity caused by plastic deformation due to impact fatigue damage. The temperature feature and the deference between damage area and non-damage area have been obtained by processing the infrared images. The results indicate that the impact fatigue damage of metallic material components can be detected qualitatively. The damage area can be identified quickly for metallic material part by using eddy current thermography.