The pseudospark switch works in the left branch of Paschen curve with low gas pressure, and it has the advantages of ns-level breakdown time, 100 kA-level pulse current and long lifetime. High pulse repetition frequency (PRF) pseudospark switch are widely used in both civil and military fields. This paper focuses on the double-pulse trigger structure and presents the design of a switch with this structure, which is tested with 10 kV anode voltage for different gas pressure, pre-trigger voltage and main trigger voltage. The corresponding relationship between the gas pressure, the two trigger voltages and trigger current are calculated respectively. In addition, the influence of pre-trigger and main trigger pulses on the trigger process is analysed. The results show that the minimum trigger voltage is only 100 V, and the switch can work stably with high repetition frequency.