To study the protective effects of flavonoid and polyphenol (FP) from lotus leaf on the damage induced by N₂O₄ in mice. Constructing an animal damage model through exposing mice to 45μl N₂O₄ in a 120 L sealed cabinet for 30 minutes. ICR male mice were randomly divided into normal group, physiological saline+N₂O₄ group,1.25g/kgFP +N₂O₄ group, 2.50g/kgFP + N₂O₄ group, 3.75g/kg FP +N₂O₄ group. 1.25, 2.50, 3.75 g/kg FP were orally administered to mice respectively for 5 days, equal volume physiological saline for normal group and physiological saline+N₂O₄ group. Then, the three FP groups and the physiological saline+N₂O₄ group were exposed to N₂O₄ in the cabinet on 5th day. In an hour after N₂O₄ exposure, killing the mice by dislocation to measure the SOD, GSH-Px activity and MDA content in lung tissue, checking pathology change in lung tissue slice. Results were shown: the 1.25, 2.50g/kg FP increased SOD (U/mg pro) by 30.3% and 24.4%, GSH-Px (U/mg pro) by 77.4% and 60.9%, respectively. Pathological observation of lung tissue showed that three FP groups had lighter damage than the physiological saline+N₂O₄ group. So, FP has significant protective effects on damage caused by N2O4 in mice.