A high-voltage and high-frequency test link has been designed for planar SiC and GaN photoconductive devices. Considering the differing characteristic impedances of wide-bandgap semiconductor devices, PSpice software was used to simulate the circuit design of the test link, while CST software was employed to simulate the high-frequency response within the 0.5~5 GHz range. The high-voltage conductivity and high-frequency response of the link were then tested using SiC and GaN photoconductive devices, respectively. Experimental results demonstrate that the proposed test link offers high voltage resistance, a fully solid-state design, and ease of disassembly. It meets the photoconductivity testing requirements of planar SiC and GaN photoconductive devices under bias voltage of 0~30 kV and within a DC~1 GHz operating frequency range. These findings provide valuable design and experimental references for evaluating the high-voltage tolerance and high-frequency response characteristics of wide-bandgap semiconductor photoconductive devices.