Abstract: The relationships of magnetization and stress at different maximum tensile stresses of 45 steel items were measured during loading and unloading. The results indicated that,when maximum tensile stresses smaller than 610MPa,the relationships of magnetization and stress are linearity,which may estimate loading condition of items. When the maximum tensile stresses is larger than 610 MPa and smaller than yield point of 653 MPa,the relationships of magnetization and stress have become fold line and the position of extremum of fold line rapidly increases to maximum. When the maximum tensile stresses are larger than yield point of 610 MPa,the change of magnetization with the stress and the position of extremum of bending line remains constant. It shows that the relationships of magnetization and stress have been obtained and the security estimate can be made for ferromagnetic items making use of magnetic signal.