Objective To Study the effect of ginsenoside Rb1 on antioxidant enzyme in mouse acute lung injury induced by A/swine/HeBei/012/2008/swine influenza virus(H9N2 SIV).Methods One hundred and ninety-five 6- to 8-week-old BALB/c mice were randomly divided into three groups, 65 in each.The mice in the control group were inoculated intranasally with an equivalent dilution of noninfectious allantoic fluid, and that of both the acute lung injury group(ALI group)and ginsenoside Rb1 group(G-Rb1 group)were inoculated intranasally with H9N2 SIV diluted in sterile saline, and in addition, the mice of the G-Rb1 group were treated with ginsenoside Rb1 10 mg/(kg·bw) by intraperitoneal injection continuously for seven days.Clinical signs and body weight loss were observed in eight infected mice of each group.At the same time, at the indicated time points after infection, histopathology of the lung was observed and the activities of T-SOD, MPO, CAT and GSH-PX were detected in the mouse lungs.Results After the first 2 days of infection, the mice of the ALI group showed depression, ruffled fur, reduced feed intake and weight loss. Furthermore, pulmonary edema, hemorrhage, and a number of inflammatory cells exuding from the pulmonary alveoli were observed in the lungs of infected mice. Lung coefficient and lung wet/dry weight ratio was increased gradually. The changes began to decline on the 8th day and tend to be normal on the 14th day. The organs of mice of the control group showed no abnormality.For mice in the G-Rb1 group, clinical symptoms were significantly improved, survival time was prolonged, and mortality was decreased. On the 4th, 6th and 8th day after infection：the activity of both T-SOD and CAT was significantly reduced(P<0.01)in the mice of ALI and G-Rb1 groups compared with that of the control group, but the index of G-Rb1 group was significantly higher than that of the ALI group(P<0.05).At each time point after infection, the GSH-PX activity was significantly lower(P<0.01)in the ALI group compared with that of the control group, but the GSH-PX activity of G-Rb1 group was significantly higher than that of the ALI group(P<0.01), with a significant difference between the two groups(P<0.01).Conclusions G-Rb1 can improve the activity of antioxidase in mouse acute lung injury induced by H9N2 SIV, and to some extent, G-Rb1 can ameliorate the acute lung injury induced by H9N2 SIV infection.