To investigate the characteristic methylation genes of pyretic arthralgia model in hot and dampness environment and the regulation effect of Baihu Guizhi decoction on this characteristic methylation genes. Plantar injection of CFA was used in hot and dampness environment to induce the pyretic arthralgia rat models. From 15th day after modeling, Baihu Guizhi decoction was given for 30 days. Foot volume was detected every 4 days after modeling, and HE staining was used to detect the histopathology of all rats' ankle joint at day 45.MeDIP-Seq sequencing method was used to detect the methylation level of knee joint synovial, and the method of difference sets was used to screen the characteristic methylation genesinpyretic arthralgia models.The contents of IL-1β, IL-17, TNF-α, EGF, IL-12p70, IL-4, IL-6 and IFN-γ in serum were measured by using suspension chips. The mRNA expression level of characteristic methylation genes was measured by qRT-PCR. The results suggested that as compared with adjuvant arthritis rat models(AA), the foot swelling and histopathology inpyretic arthralgia models (PA) were only slightly increased. As compared with normal group (NG), the wholegenome CpG island in both AA and PA groups was kept in a lower methylation state, furthermore, the methylation level was lowest in PA group; with 705 difference methylation genes in AA group and 2 418 difference methylation genes in PA group. As compared with AA, there were 1 287 difference methylation genes, including 974 down-regulated methylation genesand 313 up-regulated methylation genes. This difference methylation genes were mostly enriched in 32 KEGG pathways. Moreover, there were 52 characteristic methylation genes of PA models in promoter region, including 36 down-regulatedmethylation genes and 16 up-regulatedmethylation genes. After drug intervention, Baihu Guizhi decoction improved the foot swelling and pathological injury in PA models, significantly decreased the levels of IL-1β, TNF-α, EGF, VEGF, IL-17, IL-12p70, inhibited the mRNA expression levels of down-regulated methylation genes AHCY and RPL3, and promoted the mRNA expression levels of up-regulated methylation gene Agxt. In conclusion, unique methylation changes of synovial genes were present in PA models, and Baihu Guizhi decoction may adjust the methylation level of PA's characteristic methylation genes to achieve the therapeutic effect of pyretic arthralgia.