Objective:To evaluate the efficacy and safety of belimumab in the treatment of systemic lupus erythematosus (SLE).Methods:Retrospective analysis was made in 41 patients with SLE who were treated with belimumab in our hospital. The demographic data, clinical features, laboratory test results and treatment-related adverse events (AE) were collected and analyzed. Paired sample t test and Wilcoxon test were used to compare and analyze the changes of laboratory indexes before and after treatment. Results:The follow-up time of the 41 patients was (3.0±1.0) months, and 19 patients stopped belimumab because of the Covid-19 pandemic, the duration for belimumab withdrawal was (2.6±0.9) months. The most common clinical manifestation was impaired renal function (63.4%, 26 cases), followed by musculoskeletal impairment (58.5%, 24 cases). Before and after treatment, the dose of glucocorticoid was significantly decreased [15(9, 35) mg/d vs 13(8, 25) mg/d, Z=-3.573, P<0.01], the systemic lupus erythematosus disease activity index (SLEDAI)-2000 was significantly decreased [5(4, 8) vs 2(2, 4), Z=-4.446, P<0.01], the anti-double-stranded DNA (dsDNA) antibody [enzyme-linked immune-sorbent assay (ELISA)] level was significantly decreased [96(26, 300) vs 36(10, 139), Z=-3.436, P<0.01], the complement C3 level was significantly increased [(0.62±0.22) g/L vs (0.74±0.20) g/L, t=-5.454, P<0.01], the complement C4 level was significantly increased [(0.13±0.07) g/L vs (0.17±0.07) g/L, t=-5.851, P<0.01), the hemoglobin level was significantly increased [(117±15) g/L vs (125±16) g/L, t=-4.236, P<0.01) and A/G level was significantly increased [(1.30±1.36) vs (1.49±0.29), t=-5.174, P<0.01]. Four patients (13.8%) had adverse events during treatment with belimumab, including 1 case of upper respiratory tract infection, 2 cases of urinary tract bacterial infections and 1 case of herpes zoster. Conclusion:Belimumab is safe and effective in the treatment of SLE. It can significantly reduce the dosage of glucocorticoid and improve anemia, but the specific mechanism needs to be further studied.