Abstract: The relationships of magnetization and stress with different maximum stresses of 35 steel items were measured, during process of extension and shrinkage. It indicated that when the maximum stresses was higher than 255 MPa and lower than 496 MPa, the relationships of magnetization and stress were linear. When the maximum stresses was higher than 535 MPa and lower than 611 MPa, the relationships of magnetization and stress became a broken line and the position of extremum of the line was at about 150 MPa. When the maximum stresses was between 637 MPa and 662 MPa, the position of extremum of the relationships of magnetization and stress was at about 382 MPa and the change of magnetization with the stress was increasing. When the maximum stresses was up to 687 MPa, the position of extremum of the relationships of magnetization and stress moved to 458 MPa approximately and the change of magnetization with the stress was increasing too. It showed that the relationships of magnetization and stress were obtained and that one might be able to estimate the safety for ferromagnetic items by using magnetic signal.