The invention relates to the fields of large-scale cold rolling, silicon steel, galvanized wire production and the like in Chinese ferrous metallurgy industry and specifically relates to a high handling capacity nitrogen purifying device and method for the ferrous metallurgy industry. The high handling capacity nitrogen purifying device is mainly characterized by comprising a mechanical device and a control system; the mechanical device comprises a raw material gas inlet, a gas-water separator, an inlet trace oxygen analyzer, a mass flow controller, a program-control valve, catalytic deoxygenators, two deoxidation dryers or more, a valve water cooler, a product gas outlet and a hydrogen inlet which are communicated with each other. According to the high handling capacity nitrogen purifying device disclosed by the invention, hydrogen content exceeding standard in nitrogen is controlled; meanwhile, other impurities of O2, H2O, CO2 and the like are deeply removed; thus, the problem that gas impurities affect iron and steel industry product quality stability to cause quality declining of products of cold rolled steel plates, galvanized steel plates and the like is solved.