Objective: To discuss the inhibition mechanism of ursolic acid on inhibiting the growth of human carcinoma cell SMMC-7721. Method: Human hepatocellular carcinoma cell SMMC-7721 were co-cultured with different doses of ursolic acid for 24 h and 72 h

respectively. The absorbance value was evaluated by neutral red staining method

evaluation of ursolic acid on the proliferation of hepatoma cells; and the apoptosis was detected by flow cytometry. Result: Different concentrations of ursolic acid on the proliferation of SMMC-7721 cells showed obvious inhibition effect (P<0.05 or P<0.01) with a time and dose dependent manner. The half inhibitory concentration (IC50) of ursolic acid on SMMC-7721 cell strain was 12.59 mg·L-1 and 8.32 mg·L-1

respectively. The result indicated that the apoptosis rate was up to 14.07%

ursolic acid arrested SMMC-7721 the cell strain to S by flow cytometry with a dose-dependent manner. Conclusion: Ursolic acid on the proliferation of SMMC-7721 hepatoma cell line has the obvious inhibitory action

antitumor mechanism may be related to induction of cell apoptosis and cell cycle arrest in S phase.