〔Abstract〕 Objective To investigate the changes of intestinal flora in patients with rheumatoid arthritis(RA)before and after treatment with technetium[99 Tc] methylenediphosphonate injection(99 Tc-MDP).Methods Thirty-two patients with RA were collected the fresh fecal specimens before and after they treated with99 Tc-MDP. The genome DNA of fecal specimens was extracted and the V3-V4 regions of 16 S rRNA were sequenced by Illumina Miseq platform. The sequencing results were analyzed by bioinformatics methodology.Results The Chao, observed species, Shannon and Simpson index between the two groups in Alpha diversity analysis had no statistical difference(P>0. 05), but the value in post-treatment group were increased compared with the pre-treatment group. Compared with the pre-treatment of RA, there was no statistical difference in the higher proportion relative abundance on Phylum level of the intestinal microbes of RA patients, and the relative abundance of Tenericutes decreased(P<0. 05). At the genus level, the relative abundance of Ruminococcaceae,Butyricicoccus, Christensenellaceae＿R-7＿group,Holdemaniadecreased after treatment(P<0. 05). And the relative abundances of Pasteurella,Lachnoanaerobaculum and Stomatobaculum increased(P<0. 05).Conclusion The abundance and species of gut microbiota in RA patients have some changes after treatment with 99 Tc-MDP, and the diversity increases after treatment.