Objective To study the possible mechanism of Dahuang Zhechong Wan（ DHZCW） in treating chronic myeloeytic leukemia（ CML） from the angle of cell proliferation and apoptosis. Methods Sixteen nude mice were randomly divided into blank control group and high

medium and low dose traditional Chinese medicine（ TCM） groups

with four in each. The high

medium and low dose TCM groups were given DHZCW solution with the concentration of 1. 97

0. 9

0. 45 g / ml by gavage

0. 2 ml /（ 10 g · d）

once daily for 7 days

while the blank control group received the same volume of normal saline. The medicated serum containing DHZCW was prepared on the next day of withdrawal. The MTT assay

colony formation assay and Annexin V FITC / PI method were applied to detect the impact on the proliferation of CML cell line K562

the formation of colonies and the apoptosis and cell cycle respectively by the medicated serum. Results The growth inhibition rate of the high dose TCM group on 72 h was significantly higher than that of the medium and low dose TCM group（ P < 0. 01）. The colony forming rate of all TCM groups was significantly lower than the control group（ P < 0. 01） and that of the high and medium dose TCM group was lower than the low dose TCM group（ P < 0. 01）. The apoptosis rate in early and late phase

as well as the total apoptosis rate of high dose TCM group were significantly higher than the low dose TCM group（ P < 0. 05 or P <0. 01）. Cells in G0/ G1 phase in low

medium and high dose TCM groups were significantly more than that in the blank control group

with less cells in G2/ M phase（ P < 0. 01）

which was most significantly shown in the high dose TCM group. Conclusion DHZCW could inhibit the proliferation of K562 cells and induce the apoptosis by arresting cells in G0/ G1 phase. Also

best effects achieved with high dose of DHZCW.