We evaluated the efficacy and safety of belimumab combined with the standard regimen in treating children with active lupus nephritis and found that belimumab plus standard therapy promoted rapid reduction of proteinuria, and the complement C3 and C4 levels recovered faster, although there was no difference in renal remission rate at 6 months and 1 year compared to traditional treatment alone. Here, C3 is linked to lupus nephritis.