Abstract：Objective：To discuss the effect of extract of Radix Paeoniae Alba on proliferation and apoptosis of leukemia cells and its mechanism. Methods： Leukemia cells K652 were selected as the study objects， and were divided into the control group，the extract of Radix Paeoniae Alba groups of different concentrations，namely，20 μg/mL，30 μg/mL and 40 μg/mL，the miR-NC group，the miR-564 group，the group of 30 μg/mL extract of Radix Paeoniae Alba combined with anti- miR- NC， and the group of 30 μg/mL extract of Radix Paeoniae Alba combined with anti- miR- 564. In each group， activity was detected by MTT method；apoptosis was detected by flow cytometry；the real-time fluorescence quantitative PCR was applied to detect miR- 564 expression. In each group， the expression of cyclinD1， cyclin- dependent kinase inhibitor 1A(P21)， B cell lymphoma- 2(Bcl- 2)， and Bcl- 2 associated X protein(Bax) were detected by Western blotting. Results：Compared with those in the control group，K652 cell activity，and the expression levels of CyclinD1 in the extract of Radix Paeoniae Alba groups of different concentrations were decreased(P＜0.05)；the expression levels of P21 was increased (P＜0.05)；Bcl-2 protein in the 30 μg/mL extract of Radix Paeoniae Alba group were decreased(P＜0.05)，and the apoptosis rate，Bax protein and miR-564 were increased(P＜0.05). Compared with those in the miR-NC group，K652 cell activity，and the expression levels of CyclinD1 and Bcl- 2 protein in the miR- 564 group were decreased(P＜0.05)； the apoptosis rate， and the expression levels of P21，Bax protein and miR-564 were increased(P＜0.05). Compared with those in the group of 30 μg/mL extract of Radix Paeoniae Alba combined with anti- miR- NC， K652 cell activity， and the expression levels of CyclinD1 and Bcl- 2 protein in the group of 30 μg/mL extract of Radix Paeoniae Alba combined with anti- miR- 564 were increased(P＜0.05)；the apoptosis rate，and the expression levels of P21，Bax protein and miR- 564 were decreased(P＜ 0.05). There was no significant difference being found in the comparison of each detection index between the group of 30 μg/ mL extract of Radix Paeoniae Alba combined with anti-miR-NC and the 30 μg/mL extract of Radix Paeoniae Alba group(P＞ 0.05). Conclusion：The extract of Radix Paeoniae Alba probably inhibits proliferation of leukemia cells，and induce apoptosis by up-regulating miR-564 expression.