Objective:To study the effects of astragalus and lily particles on free radical metabolism and the lung pathological change in high altitude hypoxia mice

and to investigate its mechanism. Methods:SPF mice were randomized into control group

model group

low dose group of astragalus and lily granules

medium dose group of astragalus and lily granules

high dose group of astragalus and lily granules. They were intervened by intragastric infusion once a day for 14 days. From the 15 th day

all groups except control group were exposed to high altitude hypoxia cabin after 0.5 hour of gavage treatment for 72 hours. After 72 hours

all mice were executed.The content of malondialdehyde（MDA）

the activities of total antioxidantcapacity（T-AOC）and super-oxide dismutase（SOD）in lung tissues were detected by colorimetry. Morphological changes of lung issues were observed by HE staining method. Results:Compared with those in control group

the weight of the model group was declined;the indexes of lung

kidney and heart were higher;the MDA content was increased significantly in pulmonary tissue;the pathological score and inflammatoy cells in lung tissues were both significantly increased;the SOD and T-AOC activities of pulmonary tissues were decreased obviously（P<0.01）. Compared with those in model group

the weight was increased in medium and high dose group;the SOD and T-AOC activities were both increased;the indexes of lung

kidney and heart were also decreased;the MDA contents of pulmonary tissue were decreased in medium and high dose group;the pathological score and inflammatoy cells were both decreased in lung tissues（P<0.05）. Conclusion:The astragalus and lily particles could greatly enhance the ability to resistant pulmonary edema in high altitude hypoxia environment

which might be related to the regulation of free radical metabolism.