The purpose of this study was to explore the differences in megakaryocyte progenitor ex vivo expansion between CD34+ cells derived from human umbilical cord blood (CB) and bone marrow (BM). Mononuclear cells (MNCs) were obtained from CB or BM by Ficoll-Hypaque density gradient separation. CD34+ cells were purified by magnetic cell sorting (MACS). The selected CD34+ cells were seeded in serum-free conditions stimulated with thrombopoietin (TPO), TPO+interleukin 11 (IL-11), or TPO+IL11+heparin for 14 days. Amplification product (CD34+, CD41a+, and CD34+ CD41a+ cells) immunophenotypes, megakaryocyte apoptosis rates and the DNA content were measured by fluorescence-activated cell sorting (FACS). The colony-forming units of granulocytes and monocytes (CFU-GM), burst-forming units of erythrocytes (BFU-E), and colony-forming units of megakaryocytes (CFU-Mk) were also evaluated by the colony-forming units (CFU) assay. The results indicated that CD34+ cells derived from CB showed higher expansion ability of total cell counts, CD41a+ and CD34+ CD41a+ cells than those derived from BM for all days 14 of culture (p<0.05, respectively). There were no significant differences in CFU-GM, BFU-E, and total CFU-Mk counts between CB and BM-derived CD34+ cells on day 0 (p>0.05, respectively), but CB-derived CFU-Mk seemed mainly large colonies, and the number of large colonies was higher than that from BM (p<0.05) on day 0. There were no significant differences in expansion ability of CFU-GM between CB and BM-derived cells on days 7, 10, and 14 of culture (p > 0.05, respectively), but the expansion ability of BFU-E and CFU-Mk derived from CB cells was higher than that from BM (p<0.05, respectively). There were no significant differences in apoptosis rates of megakaryocyte from two source cells for days 14 of culture. Megakaryocytes derived from CB mostly showed the 2N DNA content (>90%) for days 14 of culture, while those cells derived from BM showed the increased DNA content, and 4N, 8N or more ploidy cells gradually increased with prolonging of culture time. It is concluded that CB-derived CD34+ cells have a greater proliferation potential than that derived from BM, which is therefore proven to be a better cell source for megakaryocyte progenitor expansion in vitro.