The objective of this paper is to determine a 3/4 coil-type axial magnetic field（AMF）contact used in126 kV vacuum interrupters. The characteristics of magnetic field and the behaviors of vacuum arc are studied by means of electromagnetic simulation and arcing experiment. The AMF distribution and resistance are compared for eight contact plate slots positions and locations

diversion row. Two types of slot positions without the diversion row and one type structure with the diversion row are tested in the arcing experiment. The slot positions of contact type2 and contact type 3 are left and right

respectively. Arc current is 40 k A（rms）. Arc duration in first current half-wave is set as 9 ms. The simulation and experiment results show that the AMF is higher and more uniform for contact type 3

and it has higher diffuse arc mode duration before current zero. In the second half-wave peak current

vacuum arc is more intense between the contacts with the diversion row

which is in the concentrated mode. The anode jets begin to form and it reach the cathode. The experiment and simulation results show that the3/4 coil-type contact used in 126 kV vacuum interrupter is determined as contact type 3 without the diversion row

in which the slot position is right and the installation location is that the upper contact corresponds to the lower contact.