The utility model discloses a quick extinguishing device of rolling mill exhaust emission flue, including more than one fire alarm probe, install automatic alarm subassembly in the master -control room, be equipped with a main tributary and the ramose nitrogen gas branch pipe of more than one, second nitrogen gas hose, check valve, quick -operation joint, first nitrogen gas hose, valve switch and nitrogen gas collecting main, each fire alarm probe is installed respectively in the not same district of rolling mill flue section, and its output connects the corresponding input of automatic alarm subassembly respectively, the not same district section of each branch intercommunication rolling mill flue of nitrogen gas branch pipe, main tributary in proper order through check valve, second nitrogen gas hose quick -operation joint, first nitrogen gas hose, valve switch intercommunication nitrogen gas collecting main. It can in time discover the conflagration in the rolling mill waste gas flue, eliminates conflagration in the rolling mill waste gas flue in the initial phase, prevents fire spreading, retrieves great amount economic loss. It adopts nitrogen extinguishing, does not have any influence to equipment.