Tofacitinib is an oral selective Janus kinase (JAK) inhibitor, a targeted immunosuppressant. JAK is an intracellular enzyme that transmits signals generated by the interaction of cytokines and receptors on the cell membrane. Within the signaling pathway, JAK phosphorylates and activates signal transcription factors and transcriptional activators (STAT), thereby regulating gene expression and cytokine production. Tofacitinib penetrates the cells, targeting and blocking the JAK signaling pathway, preventing the phosphorylation and activation of STAT, and thus modulating various inflammatory factors related to rheumatoid arthritis (RA). It has become the preferred targeted option for treating RA, offering patients a new treatment choice.