A magnetic model has been proposed that describes the effects of plastic deformation on magnetisation based on the theory of magneto-mechanical effect. In the current model correlating the magnetisation with the effective field, the influences of plastic strain on the model parameters and the effective field are taken into account respectively due to the difference between elastic and plastic deformation. Meanwhile, the effective fields under loading and unloading conditions are differentiated attributing to the effects of the applied stress and residual stress on domain wall motion. The computed magnetization shows a sharp change at a rather small plastic deformation even at only 0?5% elongation but subsequently a slow decrease with increasing tension, which is in good agreement with previous experimental results. Different magnetic signal characteristics in the plastic deformation region indicate that metal magnetic memory technique could be used to characterize early damage.