Objective:To further investigate the safety and efficacy of Belimumab in the treatment of patients with systemic lupus erythematosus (SLE).Methods:All SLE patients treated with Belimumab from May 1, 2020 to February 1, 2022 in Peking Union Medical College Hospital were retrospectively collected and analyzed. The clinical manifestations, the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2000) score, and laboratory test such as levels of anti-dsDNA antibody, the medication before and after Belimumab treatment, adverse events were collected. Normally distributed data were tested using the t-test, otherwise the Wilcoxon paired signed rank test was used. Results:A total of 81 patients were enrolled in this study. The use of belimumab could significantly decrease the SLEDAI-2000 score [10.00(7.75, 12.00) vs. 4.00(3.75, 6.00), Z=-5.38, P<0.001], ESR of SLE patients [19.50(12.75, 32.25) mm/1 h vs. 14.00(7.75, 20.25) mm/1 h, Z=-3.71, P=0.003], anti-dsDNA titer detected by CLIFT [300.00 (117.00, 864.00) vs. 183.00(100.00, 471.00), Z=-4.15, P=0.001], meanwhile, increase the complement C3 [0.78 (0.62, 0.97)g/L vs. 0.69 (0.55, 0.84)g/L, Z=-4.68, P<0.001], and the complement C4 [0.12 (0.08, 0.19)g/L vs. 0.10 (0.05, 0.14)g/L, Z=-4.78, P<0.001]. We also observed that with the use of Belimumab, the dosage of Glucocorticoids decreased significantly, which were [10.00(7.50, 22.50) mg vs. 7.50(5.00, 10.00) mg, Z=-4.90, P<0.001]. In addition, the antibody of IgG, IgA and IgM decreased significantly. Only one patient stopped the administration of Belimumab due to the low level of immunoglobulin. Conclusion:Belimumab can alleviate disease activity of patients with SLE and help in safely tapering the daily dose of glucocorticoid with good safety.