Objective To study the effects of methyl iodide to synthesis function of rat liver.Methods Twenty-four male SD rats were randomly divided into 4 groups, put them into the static exposure tank. 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 content of serum total protein (TP), the content of serum albumin(ALB), the content of serum globulin (GLO) and the activity of serum cholinesterase (CHE) were measured. Results With the increase of methyl iodide concentration, the the content of TP of rats decreased. There was significant difference between experimental groups and control group,and there was also significant difference between high dose group with middle and low dose group. The content of ALB gradually decreased with the increase of the concentration of methyl iodide. There was significant difference between the experimental group and the control group, and there was also significant difference between high dose group with middle and low dose group. The content of GLO changed little with the increase of the concentration of methyl iodide,there was no significant difference between each group. The activity of CHE gradually decreased with the increase of the concentration of methyl iodide ,and there was significant difference between each group. Conclusions Methyl iodide exposure may has the effect of synthesis function of rat liver.