Magnetic field pulsers (MFP) generate a pulsed magnetic field by driving current through an inductor. These pulsers have numerous applications based on the output magnetic flux density and switching time. This investigation will explore the application of gallium nitride-based (GaN) transistor in a MFP design. Based on the advantages of GaN transistors, the investigation looks towards creating a pulser capable of producing magnetic flux density of 500 Gauss with a rise/fall time of less than 500 nanoseconds. This investigation will improve upon findings from prior pulsers designed for magneto-optic switching applications. Simulation results have shown that for a given maximum current level, the GaN transistor pulser displays steeper rise and fall time when compared to a pulser employing a Si transistor. This result further highlights the potential of GaN transistor as the switching device where rapid field switching is preferable.