[Objective] The aim of this study was to investigate the expression and effect of AID on mesenchymal stem cells of patients with steroid-associated osteonecrosis. [Methods] Bone marrow was collected from the proximal femur in patients with glucocorticoid-associated ONFH (n = 16) and patients with new femoral neck fractures (n = 16). MSCs were isolated by ficoll density-gradient centrifugation. The cells at passage 3 were digested and inoculated. There are 4 groups in this study, ONFH group, AID lentivirus vector group, empty vector group and control group. Genome DNA was extracted, then methylation at CpG islands of ABCB1 promoter was investigated by bisulfite sequencing. We also investigated cell proliferation, intracellular reactive oxygen species, mitochondrial membrane potential (MMP), the amount of AID and ABCB1 transcripts from all of groups. [Results] Sequencing demonstrated that AID lentivirus vector was successfully constructed. After transfection, the expression of AID was obviously enhanced both in mRNA and protein. AID over-expression notably promoted cell proliferation, decreased ROS level, increased MMP and AID transcripts when compared with the other groups. Hypermethylation of ABCB1 gene promoter was noted in the patients with GC-associated ONFH, which was remarkably decreased by AID over-expression. [Conclusion] AID can obviously promote MSC’s proliferation by inhibition of ABCB1 hypermethylation in GC-induced ONFH.