Abstract: Studying the magnetic memory effect and its physical mechanism of ferromagnetic items under fatigue load conditions will make great sense for practical use in industrial testing.The fatigue tests of medium carbon steel specimens were performed on fatigue testing machine,and magnetic memory signals were measured and evaluated. The characteristic distribution of magnetic signals on the surface of the specimens and the inerratic transformation of magnetic signals during testing were analyzed. Finally,the physical mechanism of magnetic memory effect engendered in the experiment was explained by ferromagnetic theories.