Abstract: Experimental researches on self-breakdown characteristics of three-electrodes repetitive gas switch, including relationship between the self-breakdwon characteristics and gas pressure, gas flow speed and electrode shape, were performed on the accelerator CHP01. The results show that the deviation of self-breakdown voltage of the switch increases greatly as gas pressure rises, and proper gas flow speed is helpful to decrease the deviation but too high gas flow speed may result in greater deviation. It is also revealed that deviation and average value of self-breakdown voltage of the switch decrease as field enhancement factor increases by adjusting the electrode shape.