To monitor the sulfur dioxide residue in star anise in Guangxi, and understand the changes of the residues by cooking.MethodsA total of 180 star anise samples were randomly collected from supermarkets, whole sale markets (including individual retail point) in Guangxi. The sulfur dioxide residues were detected according to the NY/T 1435-2007 and evaluated by GB/T 7652-2006.The changes of sulfur dioxide residue by storage time and cooking were detected. ResultsThe detection rate of sulfur dioxide residue was 42.5% in 134 samples, and the violation rate was 36.6%. The sulfur dioxide residues were in the range of 1.5-660.6 mg/kg and the median was 106.6 mg/kg. The violation rates were 27.1% and 41.9% from supermarkets and whole sale markets respectively. Sulfur dioxide residue in star anise reduced from 660 to 19.2 mg/kg after cooking.ConclusionStar anise was fumigated by sulfur in Guangxi, which indicated that the relevant departments should strengthen supervision and monitoring. The results showed that the sulfur dioxide residue in soap and star anise was greatly decreased after cooking.