The inductance gradient is the most important parameter for coilgun design. By establishing a two-dimensional finite element model, effects of four shield materials with different dimensions and distance between coils and shield on inductance gradient were investigated. The coil's current distribution and magnetic field distribution under different shields were presented. Analysis shows that the inductance gradient is affected both by material conductivity and permeability. The conductivity determines the induced eddy current in the shield. The permeability determines the degree of strengthening the main magnetic field. By reducing the distance between driving coils and shield, the magnetic materials enhance the magnetic flux better, but more eddy currents are induced in the shield conductor. By increasing the thickness of the shield, the magnetic materials enhance the magnetic flux better, but more eddy currents are induced in the conductive materials due to the decreasing resistance. In order to achieve the maximum inductance gradient, high permeability silicon steel sheets can be used as the shield, the distance between coils and shield should be reduced, and the thickness of silicon steel sheets should be as small as possible to reduce eddy current effects.