The invention discloses a technological method for producing ammonium nitrate by ammonium-containing waste gas. The technological method of the invention comprises the steps of ammonium acid neutralisation, evaporation and condensation, and treatment and recovery of neutralisation wastewater. The ammonium acid neutralisation reaction in the invention generates ammonium nitrate and discharges lotsof heat synchronously, the heat can be moved by a big enough internal circulating system in a neutraliser such that the neutralisation reaction between the ammonium-containing waste gas and nitric acid can be performed normally without causing local overheat and increasing explosion risk. The neutralisation heat generated in the neutralisation reaction can be effectively used so as to greatly reduce the consumption of steam in the whole production process. The neutralisation wastewater can be completely recovered after the treatment by an ion exchanger filled with ion exchange resin. The technology of the invention can completely recover and use the ammonium in the ammonium-containing waste gas and adequately use the neutralisation heat generated in the neutralisation reaction. The energyconsumption is low and the added value of the product is high. The invention can save 100kg of steam in the production of 1000kg of molten ammonium nitrate.