Abstract: Monoammonium phosphate (MAP) used as fire extinguishing agent and anti-combustion additive etc.requires a higher purity.MAP produced by traditional wet-process phosphoric acid (WPA) amination method is mainly applied in agriculture fertilizers and can not be used as industrial product because of high content of impurities.Industrial MAP is usually produced from thermal phosphoric acid,however,the cost is high and the pollution is severe.The method that through purification of WPA to produce MAP and by-producing fertilizer-grade MAP at the same time was studied.Results showed that the industrial MAP prepared by this method with mass fraction of phosphorus (as P<SUB>2</SUB>O<SUB>5</SUB>)&nbsp; was more than 59% and absorption ratio of phosphorus (as P<SUB>2</SUB>O<SUB>5</SUB>) was above 70%;mass fraction of available phosphorus (as P<SUB>2</SUB>O<SUB>5</SUB>) of by-produced fertilizer-grade MAP was 30%~ 40% and absorption ratio of available phosphorus was 15%~20%.