Abstract: There are some problems existed in spark test device during spark test such as no recovery of output or long recovery time of intrinsic safety power supply after short circuit, and inability to satisfy request of GB 3836.4-2010 Explosive atmospheres part 4: equipment protection by intrinsic safety “i” for power supply with soft starting function. An assist device for spark test was designed. The device structure and software and hardware design schemes were given. The device has high reliability and action precision, which solves questions of existing spark test device.