NOVELTY - An industrial nitrifying waste mixed acid is recycled by placing industrial nitrifying waste mixed acid into waste mixed acid measuring jar; placing ammonium acid carbonate into reacting axe, and placing mother liquor into reacting axe; dropping waste mixed acid into reacting axe to react ammonium acid carbonate and waste mixed acid; starting water recycling injecting pump to absorb carbon dioxide gas; and using pump to inject material liquid into crystallizing axe, in which saturated mother liquor is placed into mother liquor storing jar to return to reacting axe for recycling.    USE - Recycling of industrial nitrifying waste mixed acid used to prepare nitrogenous fertilizer.    ADVANTAGE - The method uses ammonium acid carbonate which is easy to obtain, has low investment cost, low cost for device requirement, low production cost, and avoids immediate exhaust of industrial waste mixed acid (which causes environmental pollution) by recycling it.    DETAILED DESCRIPTION - Recycling of industrial nitrifying waste mixed acid involves:    (A) preparing mother liquor, dissolving 100-200 kg ammonium acid carbonate into 800 kg water at 20-256 degrees C, and using pump to inject it to measuring jar;    (B) placing 100 kg industrial nitrifying waste mixed acid into waste mixed acid measuring jar, the waste mixed acid comprising 65-80% waste vitriol and 5-20% waste nitric acid;    (C) placing 1110-1540 kg ammonium acid carbonate into reacting axe, and placing the mother liquor into reacting axe;    (D) dropping waste mixed acid into reacting axe slowly to react ammonium acid carbonate and waste mixed acid at 10-60 degrees C, starting water recycling injecting pump to absorb carbon dioxide gas, dropping waste mixed acid, and mixing for 10-40 minutes; and    (E) using pump to inject material liquid into crystallizing axe, starting crystallizing axe jacket steam to operate flash evaporation, lowering the temperature to room temperature after the mass ratio of solid and liquid is 30-75%, and centrifugally dividing to obtain nitrogenous fertilizer, in which the saturated mother liquor which is centrifugally divided out is placed into mother liquor storing jar to return to reacting axe for recycling.