The invention discloses a system for fast treating large-flow combustible gas. The system comprises a trigger igniter, an ignition device, a mounting device and a control system. The mounting device is used for mounting and fixing the ignition device in atmosphere with the large-flow combustible gas possibly generated. A composite solid propellant grain including a large number of metal particles is arranged in the ignition device, the trigger igniter is connected with the ignition device, and a nozzle is arranged on the ignition device, and is used for spraying the high-temperature energy included metal particles. A control device transmits an ignition instruction to the trigger igniter safely and reliably through an ignition control protection circuit. The invention further discloses a method for fast treating the large-flow combustible gas. The ignition device which can spray high-temperature gas instantly is arranged around a combustible gas discharge port, and therefore the combustible gas is fast combusted in the primary forming period of combustible gas clouds, detonation of the combustible gas is avoided, and the advantages of being safe and fast in response are achieved.