Abstract: To satisfy the requirements of eddy current testing in detecting defects of carbon fiber reinforced polymer (CFRP) composites, the numerical simulation and experiment were employed to study the electromagnetic field (EMF) diffusion and attenuation in CFRP structures. A homogeneous anisotropic 3D EMF model was built to study the influence of the two different conductive behaviors at the interlaminar interface on eddy currents distribution in CFRP, and to compare the EMF attenuation under the different conductive behaviors and its relation to frequency. The results show that the behavior affects the currents in multidirectional CFRP significantly, not only changes the currents distribution, but also reduces the currents intensity, while it has little effect on the currents in unidirectional CFRP, and its distribution form is unitary. Under the two behaviors, the EMF attenuation of unidirectional plate is independent of frequency, and the currents decay quickly, while the attenuation in the other plate is proportional to the frequency variation, and the currents decay slowly. According to the law of energy conservation of EMF, it is found that resistive loss is the dominant factor affecting the currents attenuation of unidirectional plate. Finally, the eddy current experiment was used to semi-quantitatively verify the numerical simulation results and physical phenomena.