Abstract: Constructing a photoconductive semiconductor switch (PCSS)-metal coil structure, we discovered a new phenomenon of electromagnetic oscillation in vanadium-compensation semi-insulating (VCSI) PCSS. Here the PCSS responds to laser pulse and high-voltage signal while the metal coil generates an oscillating voltage pulse envelope signal. The generation of this oscillating signal is not related to the input bias voltage of the PCSS, the pulse circuit components, or the electrode structure of the PCSS, rather it is related to the output characteristic of the PCSS. This physical phenomenon can be explained using the current surge model in photoconducting antenna. Preparing ohmic contact electrode on the silicon carbide material forms the PCSS, which generates a large number of photogenerated carriers when ultra-fast laser pulses irradiate the surface of the material and Simultaneously applies a bias voltage signal between the electrode. At this time inside the PCSS the electric field causes the transient current, radiating electromagnetic wave to the metal coil to generate oscillating signal.