Objective To observe the effect of Wenhua Juanbi Recipe (WJR) on the expres- sions of DNA methyltransferases (DNMTs) in peripheral blood mononuclear cells (PBMCs) of collagen- inducing arthritis (CIA) , and to study its mechanism for treating CIA. Methods Totally 90 Wistar rats were randomly divided into the model group (n =80) and the normal control group (n = 10). Rats of the model group were injected with type II collagen of bovine (BC II) emulsion from the tail to establish CIA model. Successfully modeled 50 CIA rats were randomly divided into five groups, i.e., the model group, the methotrexate (MTX) group, the low dose WJR group, the middle dose WJR group, the high dose WJR group, 10 in each group. Rats in the model group were administered with normal saline by gastrogavage, once per day. Rats in low, middle, and high dose WJR groups were administered with WJR by gas- trogavage at the daily dose of 22. 9, 45. 8, 68. 7 g/kg, respectively (once per day). Rats in the MTX group were administered with MTX suspension (0.78 mg/kg) by gastrogavage, once per week for 30 successive days. The paw swelling was evaluated using volume method (draining volume). PBMCs were extrac- ted from each group after intervention. mRNA expression levels of DNMTs (DNMT1 , DNMT3a, DNMT3b) were detected by real-time quantitative PCR. Results Compared with the normal group, the paws were obviously swollen in the model group (P <0. 01). Compared with the model group, swollen paws were obviously alleviated in low, middle, and high dose WJR groups, and the MTX group (P <0.01). Compared with before treatment in the same group, swollen paws were obviously alleviated in low, middle, and high dose WJR groups, and the MTX group (P <0. 01 ). Compared with the normal group, expression levels of DNMT1, DNMT3a, and DNMT3b in PBMCs were obviously lowered in the model group (P <0.01). Compared with the model group, expression levels of DNMT1 , DNMT3a, DNMT3b in PBMCs were obviously elevated in low, middle, and high dose WJR groups, and the MTX group (all P <0. 01). There was no sig- nificant difference in expression levels of DNMT1, DNMT3a, or DNMT3b in PBMCs among low, middle, and high dose WJR groups (P>0.05). Conclusions Expression levels of DNMTs in PBMCs of CIA rats decreased. WJR up-regulated the expression level of DNMTs in PBMCs of CIA rats in no obvious dose de- pendent way. One of WJR's mechanisms for treating CIA might be up-regulating expression levels of DN- MTs, and adjusting the state of DNA methylation.