In order to investigate the effect of RNA interference silencing survivin gene on radio-sensitivity of human hepatoma SMMC-7721 cells, mRNA and protein expression of survivin gene in SMMC-7721 cells after transfection with pGenesil-survivin-HIF mediated by liposome were detected by RT-PCR and western blot respectively. Cell viability was detected by MTT assay. Cell cycle distribution and apoptosis of SMMC-7721 cells were detected by FCM assay. Radio-sensitivity of SMMC-7721 cells was determined by clonogenic assay. The results showed that mRNA and protein expression of survivin gene in SMMC-7721 cells was significantly lower than that of control and negative interference group 48 h after transfection with pGenesil-survivin (,p,<,0.05). Cell viability of pGenesil-survivin group was significantly lower than that of control group (,p,<,0.05 or ,P,<,0.01). Cells arrested in the G,2,/M phase of cell cycle (,p,<,0.001) and percentage of apoptosis was significantly higher than that of control group 48 h after transfection with pGenesil-survivin (,p,<,0.001). ,D,0, of SMMC-7721 cells after transfection with pGenesil-survivin decreased and its radio-sensitivity increased. The radio-sensitization ratio was determined to be 1.24. These results can be suggested that silencing survivin gene enhances radio-sensitivity of human hepatoma SMMC- 7721 cells.