【Abstract】 Objective To explore the oxidative damage effect of methyl iodide on the liver of male rats. Methods Twenty-four male SD rats were randomly divided into 4 groups. Three experimental groups were given the methyl iodide with concentrations of 650mg/m3, 260mg/m3and130mg/m3 respectively for a week period of time. The duration of daily inhalation was 4 hours, The control group was given the same environmental conditions without exposure. At the end of the exposure，the level of superoxide dismutase (SOD) in serum and liver tissue and the activity of glutathione S transferase (GST) in serum were measured. Results Methyl iodide exposure can cause gradually increase of the SOD activity in rat serum, liver tissue and of GST activity in serum. There was significant difference, between experimental groups and control group. There was also significant difference among the low dose group, middle dose group and high dose group in the serum level of GST, Conclusions Methyl iodide exposure has the effect of oxidative damage on rat liver.