To explore the effects of bone marrow cells expanded under different conditions on hematopoietic reconstitution, in the liquid expanded cultural system with several cytokines and/or bone marrow stromal cell layers, the BMMNC of mice were expanded for 5 days. Then the expanded cells were transplanted into the lethal-dose irradiated mice via the caudal vein. The hematopoietic reconstitution of transplanted mice were evaluated by detecting the number of bone marrow nuclear cells and various colony forming cells. The results showed that ex vivo expansion of bone marrow mononuclear cells mediated with cytokines under cultural conditions could not improve the hematopoietic engraftment in post-irradiated mice, but the expansion supported by bone marrow stromal cells could benefit the reconstruction significantly regardless of addition with cytokines. In conclusion, the ex vivo hematopoietic cell expansion supported by bone marrow stromal cells can maintain the properties of the hematopoietic stem/progenitor cells for hematopoietic reconstitution.