The change regulation of the content chemical functional group in tremella samples with different setting levels of sulfite content was explored by using the infrared spectroscopy, and the mechanism of bleaching was further revealed. A rapid quantitative method testing the sulfite residue in tremella would be established. Moreover, the true content of sulfite content was detected by biodine drop method. The infrared spectra of the samples with different levels of residual sulfur were collected and analyzed, and the quantitative detection model based on partial least squares（PLS）was builded. The result indicated that the sulphur fumigation bleaching tremella through destroying the hydroxyl radicals of vitamin B₂. Moreover, IR quantitative prediction model for sulfite residue in tremella based on PLS has been established with R of 0.980 4 and RMSECV of 0.97. This approach showed well potential to provide a rapid, nondestructive and quantitative method for detecting the sulfites residue in food.