Abstract: The experiment selects different thickness of the 30CrMnSiNi2A flat notched specimens,which experiment with low cycle fatigue testing under the stress of 0. 7σ_s level, and conducts a two-dimensional magnetic memory testing, researchs the variation of magnetic memory signal under different cycles and different thickness. The experimental results show that: with the increase of the number of cycles, the characteristics of the magnetic memory signal of local stress concentration become more and more obvious, and the signal amplitude is also growing, the most significant characteristic phenomenon appears before the unstable crack fracture, which the normal component exists zero point, while the tangent component has max. The Logistic curve of the equivalent area of the closed field of the Lissajous synthesized by the differential of the normal and tangent component with cycles was fitting, it can be used to quantitative analysis the degree of fatigue damage. These results will provide technical support for further research on 2D testing of magnetic memory.