Abstract: This article made a review of methods used in capturing electronic system high power electromagnetic(HPEM ) effects tested on IC, PCB, and system level, and proposed that by monitoring voltage waveform at critical nodes of electrical circuits, various error effects could be monitored, classified, traced and determined for unmanned aircraft HPEM susceptibility test. A voltage probe with high input impedance as well as fiber optical output port was designed and achieved to satisfy special requirements of this application, which showed tested characteristics of 1 M input impedance, DC-450 MHz bandwidth and compact size. Working voltage waveforms at nodes of rudder control circuit, RF link circuit et al of an unmanned aircraft were remotely monitored with this voltage probe. Coupled pulse voltage waveforms at circuit nodes were successfully probed in high field strength HEMP range test of an unmanned aircraft, which showed reasonable characteristics.