Abstract： Objective To observe the effect of Buzhong Yiqi Decoction on alleviating intestinal mucosal injury in rats exposed to hypoxia at high altitude.Methods Eighteen 7-weeks-old male Wistar rats were randomly divided into the control group,the hypoxia-exposed group and the Buzhong Yiqi Decoction intervention group,with 6 rats in each group.After gavage for 7 days,all the animals in each group were exposed plateau hypoxia at high altitude to induce intestinal mucosal injury in a low pressure oxygen chamber at an altitude of 6,000 meters,except the rats in the control group.The changes of body mass and food intake of rats were recorded.Hematoxylin-eosin(HE)staining was used to observe the morphological changes of jejunum,the levels of myeloperoxidase(MPO)and diamine oxidase(DAO)in serum of rats were detected by biochemical method,and the level of gastrin(GAS)was detected by enzyme-linked immunosorbent assay.The level of reactive oxygen species(ROS)in jejunum was detected by Dihydroethidium(DHE)staining.The levels of serum superoxide dismutase(SOD),glutathione peroxidase(GSH-PX)and malondialdehyde(MDA)were detected by TBA and colorimetry.Western blot(WB)was used to detect the protein expressions of tight junction proteins Claudin-1,zona atresia-1(ZO-1)and Occludin in jejunum.Results Compared with the control group,the weight and food intake of rats in the hypoxia-exposed group were decreased significantly(P<0.05),and the ratio of jejunum villi height and the depth of crypt were decreased significantly(P<0.05).The levels of DAO and MPO,the indexes of intestinal barrier injury,in serum of rats were significantly increased and the secretion of GAS was decreased(P<0.05).The level of lipid peroxidation(MDA)in serum of rats were increased,and the antioxidant capacity(SOD,GSH-PX)were decreased significantly(P<0.05).The expression levels of Claudin-1,Occludin and ZO-1 in jejunum were decreased(P<0.05).Compared with the hypoxia-exposed group,the villi length and crypt depth of the Buzhong Yiqi Decoction intervention group were recovered(P<0.05).The contents of DAO and MPO in serum of rats were decreased significantly,while the secretion of GAS was increased(P<0.05).The contents of SOD and GSH-PX in serum of rats were significantly increased,while the level of MDA was decreased(P<0.05).The expression level of tight junction protein in rat jejunum increased significantly,and the differences were statistically significant(P<0.05).Conclusion Buzhong Yiqi Decoction can significantly improve intestinal mucosal injury caused by low pressure and Hypoxia exposure at high altitude,which may be related to improving oxidative stress injury and increasing the expression of tight junction protein in intestinal mucosa.