Effects of 7 contact design parameters on magnetic field characteristics of vacuum interrupters with cup type axial magnetic field contacts are studied by using 3D finite element method. The results show that:{1}Axial magnetic flux density weakens with increasing contact diameter or contact gap. Increasing sweep angle of coil segments or quantities of coil segments can strengthen it. Other design parameters such as slope angle of coil segments

contact plate slots quantities and contact material using CuCr50 or CuCr25 have little influence on it.{2}Phase shift time changs little when design parameters vary in a wide range.{3}Maximum current density in cup or contact plates becomes smaller by increasing contact diameter or contact plate slots quantities

decreasing sweep angle of coil segments

choosing an appropriate slope angle of coil segments or a proper quantity of coil segments

or using CuCr50 contact material.{4} Conductor resistance of contacts decreases with increasing contact diameter or slope angle of coil segments

decreasing sweep angle of coil segments or quantities of coil segments

decreasing contact plate slots quantities or using CuCr25 contact material.