Objective：To explore the method of using 5-bromo-2-deoxyuridine（BrdU） to label human umbilical cord mesenchymal stem cells（hUC-MSCs），and to explore its effect on cell proliferation and apoptosis. Methods：HUC-MSCs were isolated and cultured by direct adherent method，then the surface marker and potential ability of multi-direction differentiation were analyzed .The fifth passage of cells were labeled with BrdU at concentrations of 10，15，20，25 ?滋mol/L，excluding BrdU as control group. Cells were culti－vated respectively for 24，48，72，96 h. Trypan blue testing was used to detect cell vitality，MTT method was used to analyze cell pro－liferation and AnnexinV-FITC assay was used to detect cell survival rate and apoptosis rate. Results：Trypan blue testing showed that the living cells was more than 96% and there was no statistical significance between experimental group and control group（compar－ison among different concentration groups，P=0.89；comparison among different time points，P=0.61；interaction between time and dif－ferent concentrations，P=0.89）. MTT method detected that there was no significant difference in proliferation activity between labeled cells and unlabeled cells（P >0.05）. There were differences between cell proliferation and apoptosis rate（proliferation rate，F=12.02，P<0.001；apoptosis rate，F=6.148，P=0.009）. Conclusion：The tracing method of BrdU labeling hUC-MSCs is safe and ef－fective. The best labeling concentration and time is 20 μmol/L and 72 h.
