This research is to investigate the stress-induced magnetic fields surrounding initially undemagnetized pipeline steel specimen. A series of tensile tests were carried out. The variations of magnetic fields at different positions of the specimen were measured. Analysis of the results indicates that the specimen tends to be magnetized as a magnet with a N pole and S pole at two ends with the increase of load. The possible reasons underlying the experimental results are discussed on the basis of the theory of the interaction between dislocation and domain.