Since steel cables are widely used to be crucial components in cable-stayed bridges and architectural structures, stress
measurement of the steel cables has been given serious attentions. Among the current stress measurement methods,
magnetic method seems to be the most potential one, but its application is limited because of the complex theoretical
mechanism. According to the magneto-mechanical effect, which demonstrates that magnetization in the ferromagnetic
material varies with applied stress, a theoretical model of magnetic method is proposed to perfect the theoretical
mechanism. Thus, an equation is derived about the relation between magnetization in steel cables and cable stress. In this
model, a magnetic stress sensor is designed, with a smart steel cable as a part of it, and then a cable stress measurement
system based on LabVIEW is developed. This method allows new application in non-destructive testing, such as monitoring the conditions of stayed-cable. Considering the impact of the magnetic hysteresis, positive and negative pulsed current excitation was used to demagnetize and decrease the output of heat. This method is applied to the stress measurement of prestressed steel cable in Jiangsu Fasten Nippon Steel Cable Company, the experimental results agree with theoretical assumptions, which indicates that the method is feasible and can improve the mechanical stress measurement.