This study was purposed to investigate the anti-tumor effect of ursolic acid (UA) on t(8;21) leukemia cell line kasumi-1 and its possible mechanisms. The kasumi-1 cells were treated with UA at different concentration for different duration of time. The growth inhibition of kasumi-1 treated with UA was detected by using CCK-8 test, and the morphological changes of kasumi-1 cells were observed by Wright's staining. Furthermore, the apoptosis rate of kasumi-1 was examined by flow cytometry. Lastly, the expression of AML1-ETO, KIT, MYC, CCND1, BCL-2, P53, BAX, MDM2 and protein were detected by using real-time quantitative PCR and Western blot respectively. The results showed that the UA obviously inhibited the growth of kasumi-1 cells in dose- and time-dependent manners. The apoptotic morphological changes of cells were presented when kasumi-1 cells were treated with UA for 48 hours. The apoptotic rate of kasumi-1 cells increased in a dose- and time-dependent ways, and the mRNA levels of AML1-ETO, KIT, MYC, CCND1, BCL2, MDM2 decreased in kasumi-1 cells treated with UA, as well as the protein levels. Meanwhile, UA up-regulated the mRNA and protein levels of P53 in the same manner. It is concluded that UA can exert its anti-tumor effect by inhibiting the proliferation and inducing the apoptosis of kasumi-1 cells in a dose-and time-dependent manners, that may provide the clues for a new targeting therapy to t(8;21) leukemia.