Abstract： Objective To expand hematopoietic stem/progenitor cells at large scale in magnet stirred culture system. Methods Mononuclear cells from human umbilical cord blood were cultured in serum-free medium supplemented with stem cell factor (SCF), fh-3 ligand (FL3) and thrombopoietin (TPO). The expansion fold of cells, colony-forming and expression of surface molecules were studied in magnet stirred culture by cell counting, colony-forming assay and flow cytometry. And the engraftment to non-obese diabetic (NOD)/severe-combined immunodeficient (SCID) mice and repopulation of expanded cells by magnet stirred culture were studied through transplantation. Results After culture for 7 days, the folds of total cell expansion in magnet stirred culture were higher than in static culture(P<0.01). The number of colony-forming unit-granulocyte/macrophage (CFU-GM) and erythroid colony forming unit (CFU-E) in magnet stirred culture was greater than that in static culture(both P<0.05). The primitive cells (CD34+, CD34+ CD38 or CD133+) of the expanded cells in magnet stirred culture were less than those in static culture, P<0.05. However, the CD184+ or CD62L+ expanded cells were more than those in static culture, P<0.05. There was no significant difference in survival rate between three cell transplantation groups, all P>0.05. The analysis of multilineage hematopoiesis showed that transplanted human hematopoietic cells were represented in murine bone marrow cells by detecting the percentage of human cells identified with human specific anti-CD3/19/33/34/45 MoAb by FACS and the human specific gene Alu and Cat-1 by PCR. Conclusion Magnet stirred culture favors large-scale expansion of hematopoietic progenitor cells with the hematopoietic repopulation potential in NOD/SCID mice.