Objective:To evaluate the efficacy and safety of belimumab combined with standard regimen in the treatment of active lupus nephritis (LN).Methods:It was a single-center, pre - and post-control retrospective study. The Data of active LN patients treated with belimumab combined with standard regimen in the Department of Nephrology, the First Affiliated Hospital of Sun Yat-sen University from June 1, 2020 to June 30, 2022 were collected for analyzing the renal response rate and adverse reactions after belimumab treatment.Results:A total of 17 patients were included, including 14 females (82.35%). The age of the first medication was (26.06±2.64) years old, the median time of illness before the use of belimumab was 24.00 (8.50, 48.50) months, and the recurrence times before the use of belimumab was (1.24±1.03) times. All the 17 patients underwent renal biopsy. The main pathological types were type IV in 11 cases (11/17), type Ⅲ+V in 2 cases (2/17), type IV+V in 3 cases (3/17), and type V in 1 case (1/17). The dose of glucocorticoids was (22.95±8.30) mg/d in 1 year before belimumab administration. In 12 patients with LN who completed 24 weeks of belimumab treatment plan, the 24-hour urinary protein showed a downward trend, and there was a statistically significant difference compared with the baseline at 24 week [0.49 (0.15, 2.19) g vs. 2.83 (1.14, 4.11) g, Z=-2.100, P=0.036]. Compared with the baseline, serum albumin at 24 week increased by 29.36%, with statistically significant difference [(34.50±3.34) g/L vs. (26.67±5.75) g/L, t=-3.840, P=0.030]. The systemic lupus erythematosus disease activity index-2K score continued to decline, with statistically significant difference compared with baseline at 24 week (5.00±3.02 vs. 12.00±2.82, t=6.163, P<0.001). The lymphocyte count increased, and the difference was statistically significant compared with the baseline at 24 week [0.72(0.28, 2.39)×10 9/L vs. 0.30(0.19,0.34)×10 9/L, Z=-2.073, P=0.038]. There was a statistically significant difference between the glucocorticoids dosage at 24 week and the average glucocorticoids dosage 1 year before treatment [(11.25±6.35) mg/d vs. (22.60±9.75) mg/d, t=4.225, P=0.003]. After observation of belimumab for (38.13±22.93) weeks, patients had a complete response rate of 64.71% (11/17), a partial response rate of 17.65% (3/17), and an overall response rate of 82.35% (14/17). Relapse occurred in 1 case.No infusion-related reactions occurred in 17 patients. During the treatment, a total of 5 adverse events occurred, including 2 cases of pulmonary infection, 1 case each of sepsis, upper respiratory tract infection, and cytomegalovirus infection, which all improved after treatment and the subsequent treatment was not affected. Conclusion:Belimumab combined with standard regimen can improve the response rate of LN, reduce the recurrence rate, reduce the dosage of glucocorticoids, and control the overall adverse events with good prognosis.