The invention discloses a gas injection type parallel gap device. The protection device belongs to the field of lightening protection gap for power transmission lines of alternating-current and direct-current electric power systems. The device is connected with the two ends of a power transmission line insulator chain in parallel, under a lightening stroke, the device is broken down before the insulator chain can be broken down, and thus the insulator chain and the corresponding power transmission line can be protected; moreover, a high-speed high-voltage gas flow can be generated fast and acts on arcs to restrain formation and development of the arcs, the arcs are extinguished in a transient state, and thus the lightning trip-out rate and the lightening accident rate of an electric power system are reduced. The gas injection type parallel gap device comprises arc-control devices on the grounding side and the wire side, fixing devices and parallel spiral fittings installed at the two ends of the insulator train of the line. The arc-control device on the grounding side and the arc-control device on the wire side respectively comprise an arc extinguishing powder storage chamber, an arc air-termination ring, an insulating gas generation chamber, an arc spray channel and the like. With the device, the stability of the electric power system is improved, the on-load action frequency of a breaker is effectively reduced, the service life of electric power equipment such as a transformer is prolonged, and production, operation and maintenance cost is very low.