Vacuum circuit breakers (VCB) with faster breaking speed can break the short-circuit current in a very short time, which is helpful to reduce the impact of short-circuit current on the power equipment. However, it is difficult to apply single-break VCB to high-voltage grid directly. In this paper, a novel SF₆ gas insulated 363 kV VCB is proposed, which uses the series and parallel structure of 40.5 kV vacuum interrupters. It is able to cut short circuit current in extremely short time by using the operating mechanism based on the eddy current driving principle. For higher voltage level VCB, it is of significance to study its internal electric field. A multi-medium 3D FEM model is established and the single and terminal unit's electric field are determined based on the simplified symmetrical structure. Then the electric field of bus bar, arc extinguish chamber and connecting terminals are analyzed. The results show that, under lightning impulse voltage, the maximum electric field is at the circular bead of connecting terminals and transfer flange, reaching at 28.5 kV/mm and 22.9 kV/mm respectively. The maximum electric field on the surface of the bus bar is 13.4 kV/mm, and electric field inside and outside the vacuum interrupter and other components are in the control range. Connecting terminals radius is optimized and its optimal value is determined to be 12 mm, which provides a reference for the prototype production.