Abstract: Objective To study the toxicological role of sulfur dioxide(SO₂)on mammalian cells and its protection.Methods After being treated sulfur dioxide derivatives(sodium hydrosulfite and sodium sulfite.3:1,mol/L)or/and vitamin C(VC)by i.p.,the activity of catalase(CAT),superoxide dismutase(SOD)and the level of lipid peroxidation(LPO)in lung fibroblast cells(CHL)in Chinese hamster were investigated.Results (1)After treated solely by sulfur dioxide derivatives,the activities of CAT of examed groups were decreased significantly at 12 and 24 h;at 36 h the decrease of activities of CAT was highly significant except 5 mmol/L group;at 48 h the activities of CAT of 15,20 mmol/L groups were still highly significant.With the exception of 5 mmol/L group at 12 h the levels of LPO of other groups had significant or highly significant increase.(2)After treated by VC,the activities of CAT of examed groups were increased significantly only at 12h;Mean-while,the levels of LPO were all decreased,and there was significant difference between 0.10,0.25mmol/L groups and their control groups at 12 h.(3)After treated synchronously by 0.1 mmol/L VC and different dose derivatives of sulfur dioxide,the activities of CAT still had the tendency of decrease.But the activities of CAT of VC groups were higher than that of none-VC groups.And the activities of 5,10 mmol/L groups at 12 h as well as 10,15 mmol/L groups at 24 h were significantly higher than that of none-VC groups.LPO levels,which arose from SO₂,were decreased by VC.(4)SOD was not be detected in this test.Conclusion Derivatives of sulfur dioxide might cause the decrease in CAT activities and the increase of LPO levels in CHL in Chinese hamster,and VC has the protection role on it.