The cavity structure of the anode and the cathode of a pseudospark switch is an important factor for its performances. When the cathode has a cavity structure, the electric erosion on the cathode and anode is small and a concentric ring-shaped erosion pattern is observed at the central area around the apertures of both electrodes. Without the cathode cavity, the erosion becomes stronger, and the patterns become irregular and unstable. Several kinds of electrode structure have been designed and investigated. Among them, a unique cavity structure of intermediate floating electrode in pseudospark switch has a good performance. This configuration could reduce the erosion on the electrodes and increase the selfbreakdown voltage of the pseudospark switches up to 80kV. In this paper, we have studied the influence of the electrode structure on the erosion of the electrode and the selfbreakdown characteristic of the switches.