The invention discloses a quick-acting bypass switch which is a gas spark switch and comprises a high-voltage electrode and a ground electrode. The quick-acting bypass switch is characterized in that: the bypass switch leads to forming of spraying plasma in a switch gap and continuous frontward development of the spraying plasma through forming the spraying plasma on the surface of the ground electrode and injecting into the switch gap; when a residual gap between the head of the plasma and a high-voltage electrode shortens continuously and leads to severe distortion of an electric field, gap discharge is caused, and furthermore conduction of a whole switch is caused, thereby realizing quick conduction of the switch. Because plasma in the switch gap provides a large amount of initial electrons for gap discharge, insulating strength of the gap is reduced, and therefore quick discharging of the switch can be triggered under an ultralow work coefficient which equals with 5%-10% self-breakdown voltage.