Abstract: A method of ICP-MS after acidification separation was developed for the determination of nine different impurities (including Al, Fe, Sn, Te, Sb, Ti, Ga, Pb, Ge) in high purity selenium. The interferences on analytes and the pollution of sample introduction system were efficiently avoided by separation impurity elements from matrix selenium by means of low boiling point of selenic acid. The influences of dosage of sulfuric acid to separation effects were studied. The variation trend of ⁷⁴Ge and ⁷⁶Ge contents with the different amounts of residual selenium in sample solution was also determined. The analytical results proved to be accurate and validated by comparison of proposed methods with SeO₂ separation and ion exchange separation. Under the optimized conditions, over 99.99% of the matrix selenium was removed by acidification separation with the acid addition was 4 mL, which eliminated the matrix effect and spectra interference in the following ICP-MS detection. The result shows that the detection limit of the method is 0.001-0.002 μg/g, the RSD is 2.5%-5.3%, and the recovery of standard addition is 90%-110%. The method is simple, applicative and suitable for the determination of impurities in high purity selenium of 99.999%.