Abstract: In view of the problem that the peak market in Nanning, Guangxi was full of sulfur star anise and the sulfur dioxide exceeded the standard,the sulfur dioxide residue in 239 batches of star anise sold in Guangxi Zhuang Autonomous Region was detected to understand the sulfur dioxide pollution in the star anise sold on the market. The star anise was processed by distillation, the sulfite series substances in the sample were converted into sulfur dioxide after acid treatment, received with hydrogen peroxide, oxidized into sulfate ions,determined by acid-base titration, and the content of sulfur dioxide in star anise was calculated. The results showed that the recoveries of sulfur dioxide at the addition levels of 0.152, 0.305, and 0.609 g/kg were 52.7%~91.7%, and the relative standard deviation was 3.0%~7.4%. The improved method was applied to detect and analyze the sulfur dioxide pollution of 239 batches of star anise sold in Nanning and its surrounding areas,Guangxi. Among them, the detected sulfur dioxide content above the standard limit of 0.150 g/kg was 24 batches, the highest was 0.839 g/kg and the lowest was 0.173 g/kg. The overall pollution level of sulfur dioxide residues in star anise in Guangxi was not high, but individual excesses still existed.

Key words: star anise（Illicium verum Hook.f.）, sulfur dioxide, automatic sulfur dioxide analyzer, pollution, Guangxi Zhuang Autonomous Region