Abstract: Objective To observe the effect of stable and transient transfection with RNAi on expression of AFP in hepatocellular carcinoma（HCC） cell line EGHC-9901. Methods siRNA expressing plasmids targeting the AFP gene were constructed,and stably and transiently transfected into HCC cell line EGHC-9901.Expression of AFP mRNA and protein was detected by semi-quantitative RT-PCR and Western blot,respectively.Effects of the two transfection methods on AFP expression were compared by Grayscale analysis. Results Among the monoclonal cells derived from G418,the expression of AFP was significantly inhibited.Western blot and RT-PCR assay showed that the inhibitory rate of stable and transient transfection was 84.3% and 89.7%,respectively,for the expression of AFP protein and mRNA,and the inhibitory rate of transient transfection was 28.5% and 34.2%,respectively,for the expression of AFP protein and mRNA. Conclusion siRNA expressing plasmids targeting the AFP gene can be stably transfected into HCC cell line EGHC-9901.The AFP gene is significantly inhibited.The inhibitory rate of stable transfection is much higher than that of transient transfection for the expression of AFP protein and mRNA.