Abstract: Chemical precipitation method was employed to remove the impurities,such as aluminum,magnesium,and fluorin from the wet-process phosphoric acid.Ammonium nitrate and hydrofluoric acid were adopted to precipitate aluminum and magnesium impurities in the form of an easily separable phase:(NH<SUB>4</SUB>)<SUB>x</SUB>Mg<SUB>y</SUB>Al<SUB>z</SUB>(F,OH)<SUB>6</SUB>·2H<SUB>2</SUB>O.From the chemical molecular formula,it′s perceptible that the content of aluminum,magnesium,and fluorin affected the formation of this complex obviously.Therefore,three variables (addition amount of ammonium ion,aluminum ion,and fluoride ion) were used for making orthogonal regression experiment design.It was concluded that the amount of aluminum in acid was the limiting factor of magnesium precipitation.Thus complete removal of magnesium,which was a major impurity in wet-process phosphoric acid,can be obtained by adding extra soluble aluminum salt simultaneously with hydrofluoric acid and ammonium nitrate.Finally,optimum reaction conditions after several experiments were obtained and the impurity removal effect was also very good.Thus,it was significant to use this method to remove impurites from wet-process phosphoric acid.&nbsp;