The invention discloses a gas spark switch for a high voltage nanosecond pulse sterilizing system, which comprises a discharge main electrode, an anode support, a triggering pin electrode, an insulating layer and a switch housing, wherein the switch housing consists of a rear end cover, a metal casing and an output section housing; the metal casing is fixedly connected with the output section housing by connecting bolts; electrode gap adjusting bolts are arranged on the end cover; the tail end of the triggering pin electrode is fixedly connected with a triggering pin fastener; external threads are formed on the triggering pin fastener; internal threads matched with the external threads are formed on one side of an insulator; and the triggering pin fastener is screwed on the insulator in a threaded manner, so that a distance between the tip of a triggering pin and the main electrode can be adjusted. According to the gas spark switch for the high voltage nanosecond pulse sterilizing system, the gap of the main electrode is small, the spark inductance is smaller, and an electric field distorts acutely in a conducting process of the switch, so that the conducting speed of the switch is high, and the spark resistance is small.