Axial magnetic field (AMF) characteristics of coil type AMF vacuum interrupters are analyzed by 3D finite element method. Seven contact parameters are taken into account in this paper. Analysis results show that: (1) Axial magnetic flux density decreases with increase of contact diameter, coil height, and gap distance. Axial magnetic flux density is not sensitive to coil thickness. So is contact plate material. Axial magnetic flux density is strongly influenced by welding of stainless steel plates to contact plate and coil. (2) Phase shift time between AMF and source current decreases with decrease of contact diameter and increase of contact gap. And it also decreases when contact material is CuCr5O. (3) Maximum current density in coils or contact plates decreases with increase of contact diameter, coil thickness. And it also decreases when contact material is CuCr25. So does conductor resistance.