Abstract: Magnesium ammonium sulfate precipitation method is used to recover high concentration of ammoniacal nitrogen in ammonia sulfate wastewater.The influences of various factors,such as the volume ratio of ethanol to solution,pH of solution,n(N):n(Mg),reaction time and seed crystal dosage on the recovery efficiency of ammoniacal nitrogen are investigated.The results indicate that the additions of magnesium sulfate and anhydrous ethanol can treat ammonia sulfate wastewater in one step.The recovery rate can reach 70.10% and the obtained crystalline product magnesium ammonium sulfate can be used as sulfur-containing fertilizer in farmland when n(N):n(Mg)=1.5,n(N):n(S)=0.9,the volumetric ratio of ethanol to solution is 1.0,reaction lasts for 5 h and the initial concentration of ammoniacal nitrogen is 2,500 mg·L-1.The addition of seed crystal cannot improve significantly the recovery rate of ammoniacal nitrogen,but the addition of some seed crystal can make the crystals agglomerate together to form clusters.Dynamics analysis shows that this reaction conforms to the Pseudo-second-order kinetics equation with a correlation coefficient of 0.998 7.