Abstract： Objective： To observe the curative effect of modified Jiedu yin combined with western medicine on rheumatoid arthritis in the knee and its effects on the expression of serum pentraxin- 3(PTX3) and CXCL13. Methods：A total of 80 cases of patients with rheumatoid arthritis in the knee were selected and divided into the study group and the control group according to the random number table method，with 40 cases in each group. The control group was treated with western medicine，and the study group was additionally treated with modified Jiedu yin based on the treatment of the control group. Both groups were treated for 24 weeks. Clinical effects and the incidence of adverse reactions during treatment were observed in the two groups. Before and after treatment，changes in Chinese medicine syndrome scores， Lysholm knee joint scores，cytokines [levels of interleukin- 4(IL- 4)，interleukin- 6(IL- 6)，interleukin- 10 (IL-10)，interleukin-17(IL-17)，transforming growth factor-β(TGF-β)，and interferon-γ(IFN-γ)]，and the expression of PTX3 and CXCL13 in serum were compared between the two groups. Results： The total clinical effective rate was 72.50% in the control group， and 90.00% in the study group， the difference being significant(P＜0.05). After treatment，the scores of joint swelling，morning stiffness，soreness and fatigue，difficult flexion and extension，cold pain，aversion to wind- cold，tinnitus and dizziness and the total scores in the two groups were decreased when compared with those before treatment，differences being significant(P＜0.05)；after treatment，the above seven scores and the total score in the study were lower than those in the control group， differences being significant(P＜0.05). After treatment， Lysholm knee joint scores in the two groups were increased when compared with those before treatment，and the score in the study group was lower than that in the control group，differences being significant(P＜0.05). After treatment，levels of IL-4，IL-10 and TGF-β in the two groups were increased when compared with those before treatment， and levels of IL- 6， IL- 17 and IFN- γ were decreased， differences being significant(P＜0.05)；levels of IL- 4，IL-10 and TGF- β in the study were higher than those in the control group， and levels of IL- 6， IL- 17 and IFN- γ were lower， differences being significant(P＜0.05). After treatment， levels of PTX3 in the two groups were decreased when compared with those before treatment，and the PTX3 level in the study group was lower than that in the study group，differences being significant(P＜0.05). After treatment，levels of CXCL13 in serum in the two groups were decreased when compared with those before treatment，and the CXCL13 level in the study group was lower than that in the study group，differences being significant(P＜0.05). During treatment，the incidence of adverse reactions was 7.50% in the study group and 10.00% in the control group，there being no significance in the difference (P＞0.05). Conclusion：Modified Jiedu yin combined with western medicine can relieve clinical symptoms of patients with rheumatoid arthritis in the knee，improve knee joint function and body immune function， and reduce expression levels of PTX3 and CXCL13 in serum.