This study was aimed to investigate the effects of recombinant human erythropoietin (rhEPO) on proliferation of human bone marrow-derived mesenchymal stem cells (MSCs) in vitro. The aspirates of the bone marrow from healty volunteers were seeded in culture medium. Then MSCs were isolated according to characteristics adhering to the plastics. After three passages in culture, bone marrow-derived adherent cells were identified by growing morphological features, cell surface antigens and differentiation into multi-lineages. Then P3-MSCs which had been identified were incubated with different concentrations of rhEPO (0.5, 1, 5, 10 and 50 U/ml). Subsequently, proliferation of MSCs was measured by MTT assay, as well as cell counts. At the same time, cell cycle was detected by flow cytometry (FCM). The results indicated that the expressions of CD90 and CD105 in P3 bone marrow-derived adherent cells were positive, while the expressions of CD34 and CD45 were negative, and these cells could differentiate into adipocytes, osteocytes and chondrocytes in induction media. MTT assay showed that the optical density (OD) of group treated with EPO was significantly higher than that in the control group (p<0.05), and the group treated with 50 U/ml EPO achieved the most predominant effects. The results of cell count were coincident with that of MTT assay. Furthermore, the cell cycle analysis by FCM revealed that rhEPO could relatively decrease the cell ratio in G0/G1 phase, and increase the cell ratio in S and G2/M phases. As compared with the control group, all those differences were statistically significant (p<0.01). It is concluded that erythropoietin can promote proliferation of human bone marrow mesenchymal stem cells in vitro, which may be correlated with the increased entry into S and M phases of cell cycle of MSCs adjusted by EPO.