In this paper, the axial magnetic field of Vacuum Interrupter (VI) has been computed. Moreover, the static, transient magnetic field and 3D electric field have been analyzed using Finite Element Method (FEM). The dynamic distributions of the axial magnetic field along the contact surface varying with interrupting instant and space have been simulated. Accordingly, the influence of the contact structure on the interrupting and insulation performance has been analyzed. The theoretical basis for optimizing the structure and investigating the interrupting capacity of the Vacuum Circuit Breaker (VCB) has been provided.