Abstract: The metal magnetic memory signal change of 18CrNi4A was studied under different tensile loads, and the quantitative relationship between magnetic memory signal and stress was investigated. The results showed that stress concentration locations could be predicated effectively according to the zero point of the curve obtained by the magnetic memory signal under loads minus the one under no load and the position of the max slope of the Hp(y) curve. The slope of the Hp(y) curve increases with the increase of stress. There was a linear relationship between the distance from the inspection point and the metal magnetic memory signal. With the increase of the tensile strength, the slope of the metal magnetic memory curve signal increased slowly at the early stage, and then increased rapidly. However, the slope of the curve began to decline after yielding, and the signal dramatically changed when the fracture happens.