The aim of this study was to investigate whether miR-181a could modulate the sensitivity of the leukemia drug-resistant cell line K562/A02 to the chemotherapeutic agent daunorubicin (DNR), and explore the mechanism of miR-181a on the DNR sensitivity of K562/A02 cells. MicroRNA microarray and stem-loop reverse transcription-polymerase chain reaction were used to detect the expression of miR-181a. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay was performed to quantify the effect of miR-181a on K562 cells growth and viability. Apoptotic cells were quantitatively detected using Annexin V/FITC and PI apoptosis detection kit. BCL-2 protein expression was measured by western blot. Luciferase reporter vector with the putative BCL-2 3' untranslated region was constructed to explore whether BCL-2 was a direct target gene of miR-181a. BCL-2 siRNA was transfected into the cell to explore the relationship between BCL-2 and DNR resistance. The miR-181a expression level was lower in the K562/A02 cells than in the K562 cells (P< 0.05). K562 cells that were transfected with miR-181a inhibitor had a significantly higher survival than K562 cells, and K562/A02 cells that were transfected with the miR-181a mimic had a significantly lower survival than K562/A02 cells (P< 0.05). miR-181a could enhance DNR-induced apoptosis in K562/A02 cells. BCL-2 siRNA transfected K562/A02 cells had decreased survival compared with the K562/A02 control group. In conclusion, miR-181a could play a role in the development of DNR resistance in K562/A02 cells and the over-expression of miR-181a could sensitize K562/A02 cells to DNR by targeting BCL-2.