In order to study the multi field coupling problem of the electromagnetic vibration of transformer core, the magnetic structure coupling relationship of transformer core is modified by the principle of strain energy. The magnetization characteristic curve of silicon steel sheet is introduced into the simulation model, and the current density in the coil and the distribution of magnetic induction intensity in the closed loop of the core are calculated to realize the coupling of electric field and magnetic field. The principle of strain energy is used to equivalent the magnetostrictive force, and the equivalent magnetostrictive force is used as the coupling variable to carry out the transient dynamic analysis of the core structure, and the vibration distribution of the core body is obtained. The influence factors of electromagnetic vibration of iron core are analyzed. The results show that with the increase of pre tightening stress, the increment ratio of magnetostriction of silicon steel sheet increases, and the vibration of iron core intensifies; with the increase of elastic modulus in the direction of lamination of iron core, the vibration of iron core decreases gradually. The simulation results qualitatively verify the influence of assembly process on the vibration of iron core.