The invention belongs to the technical field of waste gas recycling and discloses a gas recycling system. The gas recycling system comprises a recycled gas storage unit which is connected with a mixed gas circuit used for leading in to-be-recycled gas and a recycled gas discharging pipeline used for guiding out recycled gas; the mixed gas circuit is provided with a gas concentration detection unit; an emptying pipeline is further connected to the portion, between the recycled gas storage unit and the gas concentration detection unit, of the mixed gas circuit; and the system determines that the gas in the mixed gas circuit is led into the recycled gas storage unit or led into the emptying pipeline to be emptied according to a detection result of the gas concentration detection unit. The gas recycling system is simple in structure, convenient to overhaul, low in investment cost and small in occupied area, and the purposes that acetylene mixed gas in replaced and emptied gas of a generator is selectively recycled, and acetylene mixed gas which is not worthy of being recycled and not safe is discharged are achieved; and meanwhile the acetylene discharge amount is reduced, the environment pressure is reduced, and economical recycling of acetylene gas is achieved.