The invention relates to a method and a device for protecting the trigger cable of an MV pulse gas switch. The core lies in that ground protection switches are connected between the trigger cable anda trigger isolation resistor in parallel, and an extremely non-uniform field type electronegative gas gap is formed between the ground protection switches; by using the pulse breakdown polar effect ofthe extremely non-uniform field type electronegative gas gap, trigger pulse is grounded after being effectively introduced under the condition that the MV pulse gas switch is normally triggered; or under the condition that self-breakdown occurs on the MV pulse gas switch, the pulse voltage of the MV pulse gas switch is grounded so as to realize the protection for the trigger cable, and the problem of insulation breakdown due to the fact that pulse high voltage is coupled to the trigger cable in the breakdown process of the MV pulse gas switch is solved.