Abstract: In terms of the morphology and characterization of interfacial microdefect of diffusion bonded joints, a two-dimension finite element model with the periodically distributed microdefects on the interface was presented.The influences of interfacial contact ratio, width and length of microdefects on increments of resistance were analyzed by applying the electromagnetic module in ANSYS software.Results indicated that there is a hyperbolic variation between the interfacial contact ratio and increment of resistance of diffusion bonded joints.The increment of resistance is affected by both width and length of interfacial microdefects.A higher sensitivity between the increment of resistance and interfacial microdefects was observed when the interfacial contact ratio was in 20%-80%.Based on the theoretical expression of contact ratio and increment of resistance proposed by Lodge et al, a modified equation was developed to accommodate the effects of size of interfacial microdefect, which can lead to a more precise evaluation for integrity of diffusion bonded joints.