Abstract：Objective：To discuss the effect of oridonin of different concentrations on biological behavior of liver cancer cells SMMC- 7721 and mammalian target of rapamycin(mTOR)/P70S6 kinase(P70S6K) signaling pathway. Methods：Human liver cancer cells SMMC- 7721 were divided into the liver cancer group and the oridonin groups of low，medium，and high dose(low- dose group， medium- dose group， and high- dose group for short). The liver cancer group did not receive any treatment； the low- dose， medium- dose， and high- dose groups were given 5， 20， and 40 μmol/L oridonin solution respectively. Methyl thiazolyl tetrazolium(MTT) assay was used to detect cell activity in each group. Flow cytometry was used to detect rate of cell apoptosis in each group. The expression of protein and mRNA of mTOR/P70S6K in each group were detected by western blotting and PCR method respectively. Results：According to cytomorphology observation，in the liver cancer group， the cells displayed monolayer growth， accumulated on each other， and appeared morphologically spindleshaped， with a trend of continuous growth. According to cytomorphology observation，in the low- dose，medium- dose， and high- dose groups， cell morphology gradually changed； with the increase of concentration of the solution， the cell number was decreased，along with severe shrinkage of nucleus and extensive apoptosis. Compared with those in the liver cancer group，in the medium-dose and high-dose groups，the inhibition rates of cell at each time point were increased(P＜ 0.05)；compared with those in the low-dose group，in the medium-dose and high-dose groups，the inhibition rates of cell at each time point were increased(P＜0.05)；compared with those in the medium-dose group，in the high-dose group，the inhibition rates of cell at each time point were increased(P＜0.05)； the inhibition rates of cell were increased with time prolonging in the medium-dose and high-dose groups. Compared with those in the liver cancer group，in the medium-dose and high- dose groups， the rates of cell apoptosis were increased(P＜0.05)， and the expression of protein and mRNA of mTOR and P70S6K was decreased(P＜0.05)；compared with those in the low-dose group，in the medium-dose and highdose groups，the rates of cell apoptosis were increased(P＜0.05)，and the expression of protein and mRNA of mTOR and P70S6k was decreased(P＜0.05)；compared with those in the medium dose group，in the high-dose group，the rate of cell apoptosis was increased(P＜0.05)，and the expression of protein and mRNA of mTOR and P70S6k was decreased(P＜0.05). Conclusion： Oridonin can promote apoptosis of human liver cancer cells SMMC- 7721 and inhibit their activity. Lowering activity of mTOR/P70S6K signaling pathway by oridonin may be related to cell apoptosis mechanism.