The technique of electromagnetic expansion ring was widely used to study the material uniaxial dynamic tensile properties and fracture characteristics. In this paper, the ANSYS Multi-physical FEM code was used to analyze the electromagnetic expansion process of metal ring. The distribution of the inductive magnetic field, the transient electromagnetic force and the deformation act on metal ring were discussed. The results show that the radial and axial magnetic pressure are existent in early stage of excitation current. The tensil strain of the ring could be approximately assumed as uniform. The plastic strain of the ring almost achieved maximum value after one cycle excitation current and then the deformation remains under subsequent attenuating excitation.