Our study found that MET ameliorated PQ-induced ALI in rats, decreased the expression of M1 macrophage marker iNOS in the lungs, and increased the M2 macrophage marker Arg1, which suggested us that MET may attenuate the polarization of lung macrophages toward M1, and strengthened the M2 polarization. The gene discussed is ARG1; the disease is acute respiratory distress syndrome.