The magnetomechanical coupling tests were performed on Q235 steel tubular model specimens in NIM-2000HF magnetomechanical coupling equipment. The hysteresis loops were obtained in different magnetic fields and stresses. The magnetization curves were also achieved at different stresses. The influence of applied stresses on the hysteresis loops was investigated. The stress sensitive region and linear stress sensitive region of magnetic induction are determined for the model specimen according to the experimental data. The linear dependence relation of magnetic induction versus applied stresses is established, and the optimum magnetic field is determined in the stress sensitive range of magnetic induction, which builds a basis for nondestructive testing (NDT) of stress with the total magnetic flux for steel structure.