Based on the study of the three-phase disc rotation vacuum interrupter in the early stage, this paper researched on the main circuit insulation and breaking capacity of the vacuum circuit breaker for a further performance improvement, and proposed a new structure and main circuit line layout model. In this new model, the main circuit distribution was changed from the same direction to the opposite, which shortened the length of the main circuit line as well as reduced the insulation load of the main circuit. Some adjustments were also made to the position of operating mechanism, and in the case of synchronous breaking, the miniaturization design was achieved. Besides, the flexible connection mode of the conductor was changed to reduce the impact force produced between the conductive rods and the end cap and then extended the mechanical life of the circuit breaker. Based on the numerical simulation of the three-dimensional electromagnetic field, the distribution of the electric field within the vacuum interrupter has been studied. The maximum of the field strength within the vacuum interrupter and the electric field intensity distribution at the breakdown position were analyzed and calculated to optimize the design of new model. The numerical analysis of temperature field under rated current and rated short circuit current of the new miniaturization model has been verified to be feasible. The above researches showed that the new disc vacuum interrupter model not only has a guiding significance on the miniaturization design, but also provides theoretical support for further improvement of product design.