Aiming at the problem of the use of graphite gaps with different spacings, according to its working principle and combined with the Thompson theory of gas discharge, we use the 1.2/50 μs open circuit voltage wave and 8/20 μs shortcircuit current wave to test different series of graphite clearance. It is concluded that: the voltage protection level as the clearance increases with the increase of the distance, and when the gap distance is greater than 2 mm, the voltage protection level is greater than 2.5 kV stipulated by the IEC. The residual pressure, flow passage and action response time of the graphite gap all increase with the increase of the graphite order, and the gap distance is negatively correlated with the residual pressure ratio. It is verified that the multiclearance structure of the graphite gap can effectively improve the flow capacity and reduce the flow continuation. Based on the phenomenon and theoretical analysis, the design method of switch type surge protector under the condition of reasonable gap distance is put forward, which has certain reference value in practical application.