Sulfur dioxide dissolves in water to form sulfurous acid. However, sulfite is oxidizing, which can destroy the oxidase and protein of bacteria, capture oxygen in cells, and change protein structure. Sulfur dioxide can reduce the pH value of the solution and further affect the microbial activity. The sulfate radical produced by the reaction can combine with calcium ions in cells and affect microbial metabolism. Sulfite solution is a multicomponent solution with sulfate, sulfite, and sulfur dioxide molecules. Moreover, the oxidation ability of sulfite is not weak, which can completely kill microorganisms.