This study investigated the anti-hepatoma activity of different extracts from A. squamosa pericarps, phytochemistry of the ethyl acetate (EtOAc) fraction and possible anti-hepatoma mechanism of active constituents. The anti-hepatoma activity of different extracts from A. squamosa pericarps were evaluated by MTT assay against SMMC-7721 cells in vitro and verified by using H22 xenografts bearing mice. Phytochemical investigation of the active pericarp extract was carried out. The pro-apoptosis and cycle arrest effects of active constituents were observed by fluorescent microscope and flow cytometry. Western blot assay was conducted to find the possible anti-hepatoma mechanisms of active constituents. The result showed that EtOAc extract was the active fraction. Two ent-kaurane diterpenoids, named ent-kauran-16-en-19-oic acid and ent-kauran-15-en-19-oic acid, were isolated from the active EtOAc fraction. The pro-apoptosis and G1 phase arrest effects of these diterpenoids were found. Western blot assay showed that ent-kauran-16-en-19-oic acid could activate caspase-3,-8,-9, up-regulate of Bax and down-regulate of Bcl-2.