Rhizoma paridis is widely used in the traditional Chinese medicine for the treatment of cancers. Steroidal saponins, including diosgenyl saponins and the characterized component pennogenyl saponins, are regarded as the main active components of R. paridis. To date, quite a bit of research has been published which attempt to explore the in vivo anticancer effects and the underlying mechanisms of pennogenyl saponins, compounds which are present at quite low levels in the plant. In the present study, two known pennogenyl saponins (PS1 and PS2) were isolated from R. paridis axialis and identified by spectral techniques. The anti-cancer activity of these two pennogenyl saponins was investigated in nude mice bearing human hepatocellular carcinoma (HCC) HepG2 xenografts. PS1 or PS2 (purity >98%, 1 or 3 mg/kg) was administered by intraperitoneal injection, respectively. The specimens of HepG2 xenografts were removed for mechanistic study. The current results indicated that both PS1 and PS2 dose-dependently prevented the growth of HepG2 xenografts. Western blotting analysis showed that the anticancer effects of these two monomers were associated with apoptosis induction and proliferation inhibition through activation of both caspase-dependent and caspase-independent apoptotic pathways, regulation of mitogen-related protein kinase pathway and inhibition of PI3K/Akt pathway. The present data suggest, for the first time, that PS1 and PS2 effectively inhibit human HCC progression through regulation of the signal pathways associated with apoptosis and proliferation, and have the potential for the treatment of HCC.