Abstract: Wantong Jingu Tablet (WJT), a mixture of traditional Chinese medicine, was reported to relieve the symptoms of rheumatoid arthritis (RA), but its pharmacological mechanism was not completely understood. The aim of this study was to investigate the therapeutic mechanisms of WJT for RA in vivo. The effects of WJT on joint pathology, as well as the levels of Bax, Bcl-2, caspase-3, cleaved-caspase-3, ERK1/2, pERK1/2, TNF-α, IL-1β, and IL-6 were measured using collagen-induced arthritis (CIA) rats. The intestinal flora composition and the metabolites alteration were analyzed by 16S rDNA sequencing and metabolomics method, respectively. We found that WJT ameliorated the severity of the CIA rats which might be mediated by inducing apoptosis, inactivating the MEK/ERK signals and reducing the production of pro-inflammatory cytokines. WJT, in part, relieved the gut microbiota dysbiosis, especially bacterial phylum Bacteroidetes, Tenericutes and Deferribacteres, as well as bacterial genus Vibrio, Macrococcus and Vagococcus. 3′-N-debenzoyl-2′-deoxytaxol, tubulysin B, and magnoline were significantly associated with the specific genera. We identified serotonin, glutathione disulfide, N-acetylneuraminic acid, naphthalene and thromboxane B2 as targeted molecules via metabolomics. Our findings contributed to the understanding of RA pathogenesis, and WJT played essential roles in gut microbiota health and metabolite modulation in the CIA rats.