To solve the technical problems that a laser triggering switch single-channel discharge inductance is relatively large and electrical pulse-triggered gas switch project implementation difficulty is high, and an insulation failure is easy to occur, the invention provides a laser-triggered megavolt-level low-inductance gas switch. A pretriggering gap breakdown process of the switch is triggered by laser, photoelectric isolation is realized, and the technical problems of electrical pulse triggering introduction and triggering system insulation protection are avoided; and a main gap is of a fielddistortion three-electrode structure, after discal part potential reversal of electrodes is triggered, discharge is induced due to strong electric field distortion, and thus a plurality of discharge channels are formed, thereby reducing switch inductance, and prolonging the life of the switch.