Abstract: The study aims to investigate the mechanism of Fengshining fecal microbiota transplants in the intervention of rheumatoid arthritis by ultra-performance liquid chromatography-quadrupole/electrostatic field obitrap high-resolution mass spectrometry (UHPLC-Q-Exactive Orbitrap-MS). All animal welfare and experimental procedures followed the regulations of the Medical Ethics Committee of Shanxi University of Chinese medicine. The rats were randomly divided into normal group, model group, fecal microbiota transplantation group and Tripterygium wilfordii polyglycoside group, and the collagen induced arthritis (CIA) was established. The changes of body weight and metatarpodal lesions of rats were evaluated. The serum of rats in each group was analyzed by liquid chromatography-mass spectrometry and metagenomic technology for differential metabolites and microflora. The protein expression levels of Toll-like receptors (TLR4), myeloid differentiation factor 88 (MyD88) and nuclear factor of kappa B (NF-κB p65) were detected by Western blot. A total of 13 different metabolites, including arachidonic acid, docosahexaenoic acid, 13S-hydroxyoctadecanodienoic acid and L-phenylalanine were screened from serum. Three metabolic pathways, including phenylalanine, tyrosine and tryptophan biosynthesis, phenylalanine metabolism and arachidonic acid metabolism were identified through pathway enrichment. Metagenomic analysis showed that the abundance of g_Bacteroides, g_Prevotella and p_Actinobacteria in CIA group was higher. The abundance of c_Clostridia, g_Akkermansia and s_Akkermansia_muciniphila in fecal microbiota transplantation group is higher. The hierarchical cluster heat map showed that Akkermansia was negatively correlated with L-phenylalanine; while positively correlated with docosahexaenoic acid. Prevotella was positively correlated with L-phenylalanine. Fecal microbiota transplantation group could significantly inhibit the expression of TLR4, MyD88 and p65 proteins in the synovium of rats (P < 0.01). The anti-rheumatoid arthritis effects of fecal microbiota transplantation group is closely related to the intervention of the metabolism of phenylalanine and arachidonic acid, through Akkermansia, Prevotella and other microorganisms, inhibition the TLR4/MyD88/NF-κB pathway.