Abstract: The phenomenon of magnetic memory that the magnetic leakage field generates on the surface offerromagnetic components in loading state was investigated. The stress of the plate with a hole in the center was calculated by the finite element method and the magnetic leakage field of the plate under the load of tension was measured. The results indicate that stress concentration strongly affects the magnetic properties of ferromagnetic components. Valid magnetic memory signals exist in a small scale of plastic deformation zone. It is feasible to detect the initial damage of ferromagnetic components caused by stress concentration by the magnetic memory testing method.