For impact device structure, the influences of parameters variation, such as bottom diameter, step diameter and cone bottom angle, on the geometry structure of impact device were researched, and considering the high strain rate of material and the medium hyperelastic constitutive relationship, the electromagnetic field and deformation field models were built by finite element simulation method. Then, the influences of structural parameters of impact device on the forming height, strain rate and impact velocity were analyzed. The results show that as the bottom diameter decreases, the forming height of sheet and the impact velocity of impact device increase, the forming height of no step is close to that of a small step, and the first strain rate peak value in the center of sheet increases. However, the decrease of step diameter is more conductive to improve the impact velocity of impact device and increase the forming height of sheet. When the bottom diameter is constant, the forming height tends to increase with the decreasing of cone bottom angle. When the bottom diameter is reduced to a certain extent, the influence of cone bottom angle on the forming height is not obvious.