Abstract: Based on the theory of micro-magnetism, the detection mechanism of metal magnetic memory based on the principle of minimum energy is studied. The results show that the changes in magnetic field strength of the component surface can be reflected by the change of the internal energy. The horizontal component of the magnetization intensity has the maximum value and the vertical component has obvious nonlinear change, that is, the existence of "zero crossing" phenomenon is obtained by calculating the distribution of the magnetization intensity vector in the magnetic domain fixed node of the stress concentration area. In order to further verify the theoretical analysis, the tensile test and the magnetic memory signal measurement of the flat semi-circular notch specimen were carried out. The experimental results are consistent with the theory, that is, the variation of the leakage magnetic field in the stress concentration area of the component are consistent with the change characteristics of the internal magnetization strength vector of the component, which provides an idea for the mechanism research of the metal magnetic memory detection technology.