Abstract: According to the issue of ferromagnetic material stress detecting, the relationship between the coercive force and the stress of ferromagnetic material is studied. The dctection of the stress by detecting the coercive force of ferromagnetic material is proposed. Using electromagnetic detection principle to measure the coercive force of ferromagnetic materials, three ferromagnetic rings suffered different sizes tensile stresses are selected by the experiment. On the symmetrical position of the ring around a detection coil and an excitation coil, by using sinusoidal AC signal as an excitation, the value of the coercive force of three rings is calculated by measuring the magnetic hysteresis loops of ferromagnetic ring. The results show that after the ferromagnetic material is stressed, the shape of the hysteresis loop will change.The value of the coercive force of the meterial will be increased as the stress increases. Therefore, the stress with which the material is subjected can be measured by the coercive force.