Abstract: In this paper, a switch is used as a crowbar to suppress the muzzle arc. The switch has low resistance when it is triggered. The results are compared between two experiments in which the crowbar switch is or not triggered just before the muzzle timing. When the crowbar switch is triggered, the muzzle voltage reduces obviously, almost all current flows through the crowbar switch, images obtained from high-speed photography show that the light intensity of muzzle arc is decreased visibly. It is also found that the conduction of the crowbar switch is delayed compared to the triggered signal. The delay affect the performance of the arc suppressing.