OBJECTIVE: To detect the expression level of serum B-cell activating factor (BAFF) in patients with systemic lupus erythematosus (SLE), and to investigate the relationship between Chinese medical evidence of SLE and BAFF and disease activity indicators. Methods: The serum BAFF levels of 91 SLE patients and 20 healthy controls were measured by enzyme-linked immunosorbent assay (ELISA), and the sedimentation, complement 3 (C3), complement 4 (C4), and C-reactive protein (CRP) of SLE patients were also measured. Results: 1. BAFF levels in the serum of SLE patients were higher than those in the healthy control group (P<0.01), and the levels in the SLE disease activity group were significantly higher than those in the healthy control group and inactive group (P<0.01); 2. BAFF levels in the serum of SLE patients were positively correlated with SLE disease activity index (SLEDAI) and sedimentation (r=0.671, P<0.01; r= The BAFF level in serum of SLE patients with heat toxicity was significantly higher than that of SLE patients with heat stasis and toxicity, turbid toxicity, heat toxicity burning yin, liver stagnation and toxicity, and positive deficiency and evil love (P<0.01); the BAFF level of SLE patients with positive deficiency and evil love was significantly lower than that of the other types (P<0.01). The BAFF levels of SLE patients were significantly lower than those of other evidence types (P<0.01). Conclusion: BAFF levels were significantly higher in SLE patients and correlated with disease activity indicators; BAFF levels were significantly higher in the serum of SLE patients with incandescent heat and toxicity compared with other evidence groups, and significantly lower in the group with positive deficiency and evil love compared with other evidence groups, suggesting that anti-BAFF monoclonal antibody may have different efficacy in different TCM evidence types of SLE. Exploration of the relationship between SLE TCM syndromes and BAFF and disease activity indicators