Abstract: Objective: To investigate the effects of simulated microgravity on C-fos of the pulmonary tissues in rats and the ligustrazine counter its function.Methods:Male Wistar rats were randomly assigned into 3 groups: control group,7 d tail-suspension group and ligustrazine countermeasure group（once every day,the dose is 1.5 mg/kg for one rat）.Tail-suspension（-30） was used to simulate the physiological effects of microgravity.The dynamic expression of C-fos in the lung tissue were measured by immunohisochemical technique,in-situ hybridization.Results: Compared with control group,the expression of C-fos in lung tissue were increased,and the difference had statistical significance（P＜0.01） in TS 7 d group,but the expression in the ligustrazine countermeasure group decreased significantly compared with those of TS 7 d（P＜0.01,P＜0.05）.Conclusion: The expression level of C-fos in lung tissue increased obviously in tail-suspension rats,while ligustrazine countermeasure can decrease the higher expression in TS 7 d rats,which suggested that ligustrazine could effectively prevent acute lung injury in tail-suspension rats.