A method for the analysis of fluorine, chlorine, bromine and thiocyanate in agricultural ammonium sulfate by ion chromatography was established. The samples were extracted by water, purified by Ba ion column and detected by ion chromatography. There is a linear relationship between the concentration of four anions and the peak area, the correlation coefficient r > 0.999, the recovery rate was 80.23% ~ 111.50%, and the precision (RSD) was 0.62% ~ 9.08%. When the sample weight is 0.1g, the detection limit of fluorine and chlorine is 10mg / kg, and that of bromine and thiocyanate is 20mg / kg. The method is simple, fast and reproducible,and recovery can meet the requirements of analysis, and can be applied to the detection of impurity anions in agricultural ammonium sulfate.