The mechanism of sulfur dioxide (SO₂) to inhibit gray mold disease of postharvest tablegrape by regulating sulfite metabolism was investigated. The Munage grape (Vitis vinifera L.) was fumigated with 200 μL/L SO₂， and then inoculated with Botrytis cinerea. The parameters related to fruit quality during storage and the contents of sulfite metabolites were determined. The change trends of enzyme activities， as well as the sulfite metabolism related genes were also analyzed. The effects of exogenous SO₂ treatment on sulfite metabolism pathway of postharvest grapes， and the relation between sulfite metabolism level and fruit resistance to Botrytis cinerea were discussed. The results showed that SO₂ fumigation could reduce the weight loss rate， maintain the hardness， delay the morbidity and the decrease of soluble solids and titratable acid content， and induce the increase of sulfite content as well. The contents of sulfites， H2S and Cys were significantly increased by exogenous SO₂. The enzyme activities of SiR， SAT and OAS-TL were promoted and the expression of VvSiR1、VvSAT1、VvSAT2、VvSAT5 and VvOAS-TL were also induced. It was suggested that exogenous SO₂ might enhance the disease resistance of postharvest grape to Botrytis cinerea by regulating the sulfite metabolism pathway.