Abstract: The effects and mechanism of ursolic acid (UA) on the differentiation of human leukemia cell line HL-60 was investigated in this study .The morphology of HL-60 cells changed after 96 h treatment with UA,and the NBT reduction assay preliminarily suggested monocytic differentiation of the cells. Akt was phosphorylated at Thr308 and Ser473 in HL-60 cells after treatment with UA and the nuclear translocation of active Akt was observed using immunofluorescence microscopy. A specific PI3K inhibitor LY294002 was utilized to further explore the role of PI3K/Akt pathway during the process of differentiation,and it was found that UA-induced differentiation was blocked by LY294002. In conclusion,UA could induce monocytic differentiation of HL-60 cells through the activation of PI3K/Akt signaling pathway.