Therefore, this study has the following objectives: (1) to analyze the effect of csDMARDs on differences in the abundance of gut microbiota’s bacteria; (2) to analyze the relation between the abundance of intestinal bacteria and clinical activity markers, and the serum levels of IFABP2, TNF-α, IL-10, and IL-17A, and the response phenotype to csDMARDs treatment in RA. The gene discussed is IL17A; the disease is rheumatoid arthritis.