Due to the small conductivity of CFRP and the great skin depth,the heating mode in CFRP is volumetric heating. If there is a surface defect like crack or wall thinning [23,24], it leads to distortion on eddy current distribution, as depicted in Fig. 1. The introduction of a slot in the EC path results in a diversion of the EC below thedefect, causing an increase in EC density and resultant hot spots[21]. Thus, the defect area will show the high temperature (hotspot) under reflection mode. In addition, the heat will transfer to rear side (D) as the heat diffuse. Therefore, the surface defect also shows the hot spot at rear side under transmission mode. The conductivity of CFRP is inhomogeneous because of the carbon fiber structure and multi-layer structure. Some information at surface and rear surface (such as carbon fiber structure, and surface impact