Abstract: A lateral GaAs photoconductive switch was fabricated and its conduction performance was tested. To study device damage in long-term working environment, the switch is studied operating at 8 kV, 10 Hz triggering frequency and 10 mJ triggering energy for 10⁴ times. By means of confocal laser scanning microscopy, the damage morphology of the electrode edge and between the electrodes are analyzed. It is found that the thermal damage of the anode edge was caused by thermal accumulation, and the damage of the cathode edge was caused by thermal stress. The damage morphology between electrodes is characterized and classified in detail.