Differential excitation coils and differential pick-up probes for EC-NDT are qualitatively analyzed by using 3D FEA models. Eddy current density and magnetic flux density induced by the two types of probes in a conducting plate with/without defects are simulated and analyzed. The signals of the two types of probes for different lift-off heights are also simulated. Experiments are carried out using an aluminum plate with artificial defects. It is found that the sensitivity of the differential excitation probe is higher than the differential pick-up probe from both the simulation and experimental results.