【Abstract】 Objective To explore the effects of icaritin (ICA) on proliferation and apoptosis of human hepatocellular carcinoma (HCC) Hep-G2 cells and its action mechanism. MethodsHuman HCC Hep-G2 cells were cultured in vitro. The effects of ICA on proliferation of Hep-G2 cells were detected by MTT colorimetry. Hep-G2 cells were divided into blank control group (Control)， low-dose group (2.5 μM/L)， medium-dose group (5 μM/L) and high-dose group (10 μM/L). The expression of proliferation and apoptosis related proteins (Ki-67，Bcl-2，Bax，caspase-3) was detected by Western blot. The proliferation of HCC cells in each group was detected by colony formation assay. The apoptosis of Hep-G2 cells was detected by flow cytometry. ResultsMTT results showed that IC50 of ICA for HCC Hep-G2 cells was 5.38 μM/L. Compared with blank control group，relative expression level of Ki-67 protein，clone formation rate and relative expression level of Bcl-2 protein were significantly decreased in low-dose group，while apoptosis rate，relative expression levels of Bax and Caspase-3 proteins were significantly increased (P<0.05). Compared with low-dose group，relative expression level of Ki-67 protein，clone formation rate and relative expression level of Bcl-2 protein were significantly decreased in medium-dose group，while apoptosis rate，relative expression levels of Bax and Caspase=3 proteins were significantly increased (P<0.05). Compared with medium-dose group，relative expression level of Ki-67 protein，clone formation rate and relative expression level of Bcl-2 protein were significantly decreased in high-dose group，while apoptosis rate，relative expression levels of Bax and Caspase=3 proteins were significantly increased (P<0.05). ConclusionICA can inhibit proliferation of Hep-G2 cells and promote their apoptosis. The action mechanism may be related to down-regulating Bcl-2 protein，upregulating Bax protein and enhancing caspase-3 activity.