Abstract: OBJECTIVE To observe the effect of ethanol extract of Hedyotis diffusa Willd. (EEHDW) on the proliferation and apoptosis of AML-M2 cells Kasumi-1 and its mechanism. METHODS MTT colorimetry and Hoechest staining were used to detect the effect of EEHDW on the proliferation and apoptosis of Kasumi-1 cells. Western blotting was used to detect the protein levels of Bcl-2, Bax, caspase-3, caspase-9, Cyto-C, p65, p-P65, IkBa, p-IkBa, IKKa/b, C-myc and AML1-ETO in Kasumi-1 cells. RESULTS EEHDW inhibited the proliferation of Kasumi-1 cells. The 0.04, 0.06 and 0.08 mg·mL^-1 of EEHDW could induce apoptosis(P<0.05 or P<0.01). It could significantly up regulate the expression of Cyto-C, cleaved PARP, cleaved caspase-3, cleaved caspase-9 and Bax, but decreased the expression of Bcl-2, C-myc and AML1-ETO. Meanwhile, EEHDW could increase the expression of p-P65 and p-IKBα in a concentration dependent manner. CONCLUSION EEHDW induce apoptosis of Kasumi-1 cells not only related to the regulation of Bax/Bcl-2 expression, but also relate to the activation of NF-кB signal pathway, which inhibits the expression of C-myc and AML1-ETO fusion gene.