It has been demonstrated that stromal cell precursors exist in human umbilical cord blood. After being cultured in vitro, these cells are called human umbilical cord blood-derived stromal cells (hUCBDSCs). However, the role of hUCBDSCs in hematopoiesis is still unclear. We have previously shown that hUCBDSCs are superior to human bone marrow stromal cells (hBMSCs) at enhancing the expansion of megakaryocyte colony forming units (CFU-Meg). Based on this observation, we postulated that hUCBDSCs might promote megakaryocytopoiesis. to test this hypothesis, we developed a megakaryocyte/hUCBDSC co-culture model and a hematopoietic microenvironment injury model in nude mice. We explored the ability and mechanisms by which hUCBDSCs promoted the proliferation of megakaryocytes in vitro, and we also explored their capacity to restore the hematopoietic microenvironment in vivo. As expected, hUCBDSCs were more efective than hBMSCs at enhancing the proliferation of megakaryocyte lines from HeL cells and restoring megakaryocytopoiesis in a hematopoietic microenvironment injury model in nude mice. thrombopoietin (tpo) and stromal cell derived factor-1 (SDF-1) are two of the key factors underlying this capacity. We also found that gap junction intercellular communication (GJIC) between HeL cells and hUCBDSCs might be partially absent. our data provide the first evidence that hUCBDSCs play a regulatory role during megakaryocytopoiesis, which might be important for designing treatments for patients with megakaryocytic injury.