Abstract: The magnetic domain of annealed Q235carbon steel was observed by Bitter power method.Thetransformation of magnetic domain under different strain in tension condition was analyzed.The angle between thedirection of magnetic domain and the direction of tension can be worked out with the help of SEM with EBSDanalysis system and how the angle changes with the strain was also analyzed.It can be concluded that when thestrain exceeds a certain level, the angle between the magnetic domain and stress will be stable at about 45°so itdemonstrates the orientation distribution of magnetic domains achieves.It was concluded the direction of magneticdomain was determined by the relative level of stress energy and magnetocrystalline anisotropy energy.