Abstract: This paper presents a new method for detecting the stress of ferromagnetic materials. The magnetostrictive properties of ferromagnetic materials are related to the microstructure of the material, which itself changes with its own stress state. According to the hysteresis phenomenon of ferromagnetic materials, stress is applied to the specimen, and the curve of ultrasonic signal amplitude-static excitation current corresponding to the hysteresis loop is obtained by the EMAT platform based on magnetostriction. The characteristic parameters in the curve can be extracted and the characteristic parameter-stress value curve can hence be drawn. Experimental results show that this new method can qualitatively detect the stress state of ferromagnetic materials.