It was designed that an airtight planar triggered spark-gap switch （PTS） with parallel three-electrode structure based on printed circuit board （PCB） technology， aiming to improve the working probability of exploding foil initiator systems （EFIs）， as well as to reduce the size and cost of the system. The PTS was batched-prepared with PCB technology according to the structural parameters of three electrodes， and the outline of a single parallel PCB-PTS （P³） was 13.5 mm（l）×7.5 mm（w）×2.5 mm （h）. The 3D and sectional appearances of the P³ were reconstructed via a micro computed tomography， which indicated that PCB technology could meet the machining precision. We simulated the electrostatic field distribution among the switch gap to explain the conduction process， and the theoretical self-breakdown voltage （U_SB） was figured out based on the simulation results. Most importantly， the test results of electrical performance of the switch show that （1） the about 2000 V U_SB derived from real-world measurements was slightly lower than the calculated value； （2） P³ switched reliably at 50%-95% U_SB， and there was a constant risetime of about 121.8 ns and a peak current more than 1500 A， which fit the characteristic requirements of EFIs. Finally， P³ was applied to exploding foil initiator （EFI） to verify its practicability， and it was found that HNS-IV pellets were reliably detonated under the ignition condition of 0.22 μF/1400 V.