Abstract: 【Objective】 The purpose of the study was to investigate the effects of oral administration of flunixin meglumine on the structural changes of intestinal flora of yaks, and to provide a reference basis for the scientific use of flunixin meglumine in the treatment of inflammatory diseases in Maiwa yaks.【Method】 The Maiwa yaks were orally administrated with 5% flunixin meglumine solution at a dose of 0.04 mL/kg, and the fecal samples were collected at any time within 12 h before and after administration of the drug according to the defecation situation of the animals, and the bacterial V3-V4 variable region of 16S rRNA sequences were amplified with universal primers 343F and 798R, and the microbial diversity analysis of fecal samples was performed by Illumia sequencing after the PE library was constructed.【Result】 Under the condition that the coverage rate of PE library was over 96.00%, the OTU quantity of fecal samples in each group was distributed between 1633-2435, except for the decrease in OTU number after administration in young Maiwa yaks, the OTU number of young and middle-aged Maiwa yaks and old Maiwa yaks increased to varying degrees. At the phylum classification level, Firmicutes and Bacteroidetes were the dominant phyla in the fecal flora of Maiwa yaks before and after drug administration, and the relative abundance of Proteobacteria greatly decreased after drug administration. The ratio of Firmicutes/Bacteroidetes tended to increase at varying degrees, especially in the young Maiwa yaks. At the genus classification level, except for the relative abundance of Ruminococcaceae_UCG-014 in the young Maiwa yak feces, and Prevotellaceae_UCG-004 in middle-aged Maiwa yak feces and Rikenellaceae_RC9_gut_group in old Maiwa yak feces, which did not change greatly, the relative abundance of all other genera in in the structural composition of the fecal flora of Maiwa yaks of different ages changed largely before and after administration of the drug. The actual number of OTUs observed in the fecal samples of Maiwai yaks in all groups and the Chao1 and Shannon indexes showed a tendency of decreasing to different degrees after the administration of the drug, whereas the changes in the Simpson index were not obvious. The results of multivariate statistical analysis(Kruskal-Wallis and LEfSe) showed that Bacteroidetes, Fibrobacteres, Firmicutes, Fusobazcteria aand Kiritimatiellaeota were more distinct among groups at the phylum classification level. At the genus level, there were great differences between groups mainly in theEubacterium _coprostanoligenes_group, Bacteroides, and Christensenellaceae_R-7_group.【Conclusion】 After single administration of flunixin meglumine, the intestinal flora of Maiwa yaks changes to varying degrees at the phylum and genus levels, Firmicutes and Bacteroidetes are the dominant flora, indicating that flunisin meglumine only affects the relative abundance of intestinal flora in Maiwa yaks.