In this study the small interfering RNA(siRNA) targeting human VEGF effectively inhibited the expression of VEGF in human hepatoma cell line, SMMC7721, and could dramatically decrease the tumorigenicity of SMMC7721 s.c. xenograft tumor. Chemically synthesized siRNA targeting VEGF was transiently transfected into SMMC7721 cells by lipofectamine, RT-PCR and Elisa analysis suggested that the expression of VEGF mRNA and secreted protein in SMMC7721 cells with VEGF siRNA transfection were suppressed with inhibition rates of 76.16% and 96.28% respectively compared with negative control, but the growth rate of SMMC 7721 cells with VEGF siRNA transfection was the same as the control cells. In vivo test, siRNA was injected directly into implanted tumors and the tumors volume were calculated at different time interval. Result showed that VEGF siRNA greatly inhibited the growth of tumors tissues, which was consistent with decrease of VEGF mRNA and protein compared with control. In addition, the VEGF siRNA-treated group exhibited obvious signs of necrosis compared with control.