The results show that compared with the control group, the AHR methylation level in RA patients was significantly higher, while the AHRR methylation level was abnormally reduced, which means the dysfunction of the AhR pathway’s regulation.The dynamic phenotypic balance of M1/M2 can be destroyed by the AhR-miR-142a-IRF1/HIF-1α pathway. The gene discussed is AHR; the disease is rheumatoid arthritis.