For the conventional electric current perturbation (ECP) method incapable to detect internal defects in non-ferromagnetic materials, a modified ECP method, direct current perturbation (DCP) method, is proposed. This method employs Giant Magneto Resistive sensors to probe the disturbed magnetic field signals induced by a direct current. Three-dimensional simulations were performed to investigate the variations of magnetic fields due to the perturbation of direct current surrounding defects. Experiments were also carried out to confirm the capability of inspection for external and internal defects in conducting materials. The DCP signal characteristics are obtained by numerical and experimental results, which suggest the potential of the DCP for defect characterization.