Abstract: Objective To investigate effect of single and multiple administrations of metformin on treatment of rats with ventilator-induced brain injury. Methods A total of 24 healthy adult male Wistar rats were randomly divided into 4 groups, including control group(group C, n=6), mechanical ventilation group(MV group, n=6), mechanical ventilation combined with single-does metformin group(MET group, n=6), and mechanical ventilation with multiple-does metformin group(M-MET group, n=6). Group C retained spontaneous breathing after endotracheal intubation without mechanical ventilation. MV group, MET group and M-MET group were performed mechanical ventilation. Metformin was fed 500 mg/kg in the MET group before the experiment and 500 mg/(kg·d)in the M-MET group for 4 weeks. At the end of mechanical ventilation, all rats were sacrificed for brain tissue to observe pathological changes under light microscope. Interleukin-6(IL-6)and tumor necrosis factor-α(TNF-α)of brain tissue homogenate were measured by Enzyme linked immunosorbent assay(ELISA)kits, superoxide dismutase(SOD)and malondialdehyde(MDA)were measured with kits. Results Compared with group C, MV group, MET group and M-MET group had severe pathological damage, the contents of IL-6, TNF-α and MDA significantly increased, while the level of SOD decreased significantly(P < 0.05). Compared with MV group, pathological damage of the MET and - M-MET groups were alleviated, the levels of IL-6, TNF-α and MDA significantly decreased, and the level of SOD significantly increased(P < 0.05). Compared with MET group, the levels of IL-6, TNF-α, MDA and SOD in M-MET group were significantly higher(P < 0.05). Conclusion Metformin can reduce the brain injury induced by mechanical ventilation in rats. The mechanism may be related to the inhibition of inflammatory pathway and oxidative stress, and the effect of single administration is better than that of multiple administration.