To explore the effect of different doses of thrombopoietin on proliferation of bone marrow mesenchymal stem cells (MSCs) in mice, 20 Kunming mice (35 +/- 5 g) were divided randomly into 4 groups: low-dose TPO group, moderate-dose TPO group, high-dose TPO group and normal control group (n = 5). The experimental groups were subjected to intraperitoneal injections of TPO at a dose of 25, 50, 100 microg/kg, respectively, and normal control group were treated with saline at a dose of 0.1 ml/g per day for 5 days. The bone marrow was harvested on 12 hours after the final administration. The bone marrow nucleated cells (BMNCs) were counted and seeded at a density of 10(6) cells/cm(2). The colony-forming unit-fibroblast (CFU-F) of MSCs was cultured and evaluated. The CFU-F of MSCs underwent osteo-genic induction and adipogenic induction, and cytochemical and immunocytochemical staining were performed to verify their multipotential. CFU-F and the cell percentage of CD90(+), CD105(+), CD34(+) in BMNCs were analyzed by flow cytometry. The results showed that the number of BMNCs and the cell percentage of CD90(+), CD105(+), CD34(+) and CFU-F increased obviously in TPO groups as compared with the normal control group (p < 0.05). The number of BMNCs increased most obviously in the 50 microg/kg TPO group. However, there was no significant difference in number of CFU-F between 50 microg/kg and 100 microg/kg TPO group (p > 0.05). The CFU-F of MSCs in bone marrow had their osteogenic and adipogenic differentiation potentials in vitro. It is concluded that the number of BMNCs and the cell percentage of CD90(+), CD105(+) and CFU-F increased after administration with TPO. It means that TPO can enhance MSCs to proliferate in bone marrow. However, the number of BMNCs and CFU-F can not increase with the increase of TPO dose.