To investigate the effect of dihydroartemisinin (DHA) on the BCR/ABL fusion gene in leukemia K562 cell.K562 cells were cultured in vitro. The rate of proliferation inhibition of cells treated with various concentrations of DHA were determined by using [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) method. Expression of BCR/ABL fusion gene was analyzed by reverse transcription(RT-PCR) before and after DHA treatment. Apoptosis of K562 cells was detected by flow cytometry.The growth of K562 cells was inhibited when the concentrations of DHA were 10-160 umol/L. With the added dose of DHA, the growth inhibition was remarkable, with the rate of inhibition risen from 52.76% to 94.65%. The expression of BCR/ABL fusion gene, as detected by RT-PCR after incubating the K562 cells with 20 umol/L DHA, measured as ΔCt = 4.45 ± 0.25 after 12 h and ΔCt = 5.23 ± 0.21 after 24 h, which was significantly lower compared with that of the control ( ΔCt = 4.23 ± 0.21, P < 0.05).DHA can inhibit the proliferation of leukemia K562 cells and facilitate the induction of apoptosis by downregulating the expression of BCR/ABL fusion gene.