Objective To study the probability of applying mesenchymal stem cells isolated from human umbilical cord blood (hUCB MSCs) to repair mouse skin wound in vivo. Methods hUCB MSCs isolated from full term delivery human umbilical cord blood were cultured and amplified in vitro.hUCB MSCs at passage 9 were labeled with BrdU (5-bromodeoxy-uridine) and grafted on the full-thickness skin loss wound created on the back of the severe combined immunodeficiency (SCID) mouse (treatment group), when a PBS control group was set. The wound healing rate was surveyed and compared at days 7 and 14 postoperatively. Meanwhile, the wound was biopsied at days 7, 14 and 28 after operation,and the expressions of BrdU antibody and K19 antibody were checked pathologically and immunohistochemically by HE staining, respectively. Results The wound in treatment group was healed more rapidly than that in control group (P ＜ 0.01 ). The pathological check of the biopsy sample showed that the epidermis was thicker, with more epidermal ridges in the treatment group, compared with control group.It was found that some BrdU positive cells were distributed successively on the hair follicle, the stratum basal and the spinosum layers, a few of which even expressed K19. Conclusion hUCB MSCs can be differentiated into skin tissue and cells and is possible to repair skin wound.