Objective: To observe the effect of New Bitongling (NBTL) on collagen-induced arthritis (CIA) rats and to investigate its influence on the expression of high mobility group box 1(HMGB1) mRNA in the synovial tissues. Method: NBTL extractum was made by a series of processing technology. 12 of 72 SD rats were assigned to the normal group. The CIA models were induced in other rats

then they were divided into the model group

the low-

moderate-

high-dose NBTL groups (3.2

1.6

0.8 g·kg-1·d-1) and tripterygium wilfordii Hook F (twHF) group (0.008 g·kg-1·d-1). All rats received the corresponding drugs at the day of secondary immune and continuously dosed for 21 days by intragastric administration. The joint volumes were measured

the pathological tissues were observed and HMGB1mRNA in the synovial tissues were detected by quantitative real time PCR (RTq-PCR). Result: Compared with the normal group

the joints swelling was more obvious (P<0.01) and the expression of HMGB1mRNA was higher in the model group (P<0.01). Compared with the model group

the joints swelling was improved at the 14th day (P<0.05) and the 21th day (P<0.01) and the expression of HMGB1mRNA in the synovial tissues decreased (P<0.01) in the NBTL group at high dose. The pathological section of joints showed the lesions were improved in the all doses of NBTL and twHF groups as compared with the model group. Conclusion: NBTL could reduce joints swelling of CIA rats and inhibite the expression of HMGB1mRNA in the synovial tissues. The mechanism for therapy on rheumatoid arthritis of NBTL may be related to inhibiting the activation of inflammatory pathway through decreasing HMGB.