Objective: To evalute the expression of RAG and BCR gene rearrangement in mature peripheral B lymphocytes in Takayasu arteritis, reveal the possible mechanism of humoral immune response in Takayasu arteritis. Methods: Patients with Takayasu arteritis (10 cases) and healthy volunteers with age and sex matching (10cases, as control group) from Beijing Shijitan Hospital, Capital Medical University , and Peking Union Medical College Hospital from 2022 to 2023 were included in this study. The recombinant activating gene mRNA test uesd real-time quantitative PCR (RT-PCR) . Western blot was used to detect the expression levels of the RAG protein . The NGS gene sequencing technology was performed for the B cell receptor (BCR) gene sequencing. Results: The expression level of RAG1 mRNA and RAG2 mRNA in peripheral mature B lymphocytes in TA patients was significantly higher than that of normal controls（RAG1 5.56±1.71 vs. 1.94±0.86, P＜0.05; RAG2 5.26±1.59 vs. 1.65±0.64, P＜0.05）, respectively; The expression level of the RAG1 protein and the RAG2 protein in peripheral mature B lymphocytes in TA patients was significantly higher than that of normal controls（RAG1 4.33±1.58 vs. 1.52±0.59, P＜0.05; RAG2 4.67±1.88 vs. 1.59±0.56, P＜0.05）, respectively. The number of peripheral B lymphocyte BCR clonotypes in the group of patients with TA was significantly higher than in the normal control group（1574±317.7 vs. 801.3±202.1, P＜0.05）. The abundance of the BCR gene V region in TA patients was higher than that in the normal control group（31.185% vs. 13.449%）.The abundance of genes in the BCR V region was positively correlated with RAG1 and RAG2 (correlation coefficient r=1.00, P<0.05), respectively. Conclusion: High expression of the RAG gene in mature peripheral B lymphocytes may cause BCR secondary gene rearrangement in mature peripheral B lymphocytes in patients with Takayasu arteritis, suggesting that there is a possibility of secondary gene rearrangement in TA and providing important clues for the potential diagnostic indicator and therapeutic target of Takayasu arteritis, and further exploration and analysis is required for larger samples.