Abstract: A multi-gap gas switch was designed for the LTD stage to replace the switch which has a high self-breakdown probability at the voltage over 80 kV. The shape of the electrode was designed to be circularity due to the electric field simulation of the electrode. The total length of the switchs gaps was increased from 28 mm to 36 mm while the number of the gaps increased from 4 to 6. The distortion ratio of electric field was 3.98 when the switch was charged to 100 kV and triggered by 100 kV. The self-breakdown voltage testing has been conducted and the relation between self-breakdown voltage and gas pressure was obtained when the switch was filled with dry-air. As the pressure changed from 0.10 MPa to 0.20 MPa, the self-breakdown voltage increased from 103 kV to 194 kV. The experimental results of triggering feature show that the new switch had 40.1 ns delay with 1.3 ns jitter operating at 90 kV which was 60% of the self-breakdown voltage.