Abstract: Pseudospark switch is a kind of low-pressure pulse discharge switch operating on the left half branch of Paschen curve. It has the advantages of high withstand voltage, large current capacity, wide working range, long life, small jitter, etc. Therefore, it has a very large application prospect in pulse power devices. In this paper, a sealed-off double-gap pseudospark switch was developed. The ceramic-metal welding seal was adopted. A surface discharge trigger system consisting of a modified nanosecond pulse generator based on avalanche transistors and a trigger unit based on BaTiO₃ with high dielectric constant has extremely high stability. Moreover, the discharge characteristics of pseudospark switch was studied. The effects of trigger energy, anode voltage, and the filament current on the trigger delay, jitter, and the rate of voltage drop were studied. The results show that the high stability of trigger system can guarantee the low jitter of trigger delay, and the jitter can be reduced to less than 1 ns in the pseudospark switch with a clearance distance of 2.5 mm. The drop rate of anode voltage is influenced by the development process of superdense glow discharge, and is independent of the process that occurs inside the hollow cathode. Therefore, it is determined by anode voltage and operating pressure. In addition, the reasons why current is quenched in the process of pseudospark conduction are analyzed, and may be the production rate of electrons is lower than consumption rate, thus the process of forming discharge channel reversely is blocked. And some measures are taken to alleviate it.