The SN/T 5350.2-2021 standard specifies a method for the determination of arsenic in sulfur by microwave digestion and Atomic fluorescence spectrometry, AFS. This method is suitable for the determination of arsenic content in sulfur in the range of 0.5 mg/kg to 250 mg/kg. During the test, the sulfur sample is microwave digested, and the pentavalent arsenic is reduced to trivalent arsenic using thiourea and ascorbic acid, and then further reduced to hydrogen arsenide using potassium borohydride. It is then loaded into an Atomizer by argon gas, analyzed as atomic arsenic, and produced by excitation of a special arsenic Hollow cathode lamp. Fluorescence intensity is proportional to arsenic concentration, and arsenic content can be quantitatively determined by comparison with the standard series. This standard provides a reliable method for the accurate determination of arsenic in sulfur.