Abstract This paper presents the changes of both residual stress and micro-structures caused by the pulsed magnetic field treatment for mid-carbon steel. The average plastic deformation is also measured through strain gauges. After treatment about 12–24% stress is released and there is remarkable plastic deformation within grains. However, the average plastic deformation in the range of the strain gauges appears nearly to be zero, which is different from the behavior of plastic deformation in heat treatment. These experiment results suggest that the selectivity of plastic deformation associated with magneto-plastic effect, which manifests itself in migration of dislocations in crystals exposed to magnetic fields and is determined by both fields and material itself, is the essential feature of magnetic field treatment that distinguishes itself from heat treatment.