Aim To investigate the proliferative effect and the apoptosis of human hepatoma SMMC-7721 cells induced by gallic acid ( GA ) , and its underlying mechanism. Methods SMMC-7721 cells were cul-tured in vitro. MTT assay was used to observe the pro-liferation of SMMC-7721 cells induced on GA 24 , 48 , 72 h. The morphological and ultra structural changes of the SMMC-7721 cells were observed by inverted micro-scope and transmission electron microscope respective-ly. Annexin V-FITC/PI staining was used to quantify the percentages of apoptosis in the total cell popula-tion. The expression of p53 mRNA was investigated by RT-PCR. Western blot was used to determine the pro-tein expression of p53. Results GA(6. 25~50 μmol ·L-1 ) markedly inhibited the activity of proliferation and induced apoptosis of SMMC-7721 cells after 48 h in a dose-dependent manner. GA significantly induced cell nuclear condensation and fragmentation. RT-PCR and Western blot results showed that GA could improve the expression of p53 mRNA and protein. Conclusion GA can inhibit the proliferation of human hepatoma SMMC-7721 cells and induce cells apoptosis. The mechanism may be associated with improving tumor suppressor gene p53 expression.