Abstract: To study the functions of survivin gene further，three siRNA segments （S1，S2,，S3）specifically targeting survivin were selected.Accordingly RNAi plasmids pTet-U6-S1，pTet-U6-S2，pTet-U6-S3 were constructed.The changes of survivin expression were examined by semi-quantitative reverse transcription polymerase chain reaction （RT-PCR）and Western-blot analysis after the plasmids had been transfected into HeLa S3.The results show that survivin expression is inhibited at both mRNA and protein levels after the plasmid pTet-U6-S3 has been transfected,，which targets on the 3’non-encoding region of surviving.The inhibition level is much higher than that of S1 sequence reported previously.Compared with that of the control，the inhibition ratios of S1，S2，S3 to mRNA of survivin are 20%，12.5% and 40% respectively，and 39.2%，17.0% and 58.6% to its protein.And the effect of the plasmid pTet-U6-S3 on the cell apoptosis was analyzed by flow cytometry.The apoptosis of HeLa S3 cells was greatly increased after transfection for 48h.

Key words: survivin, RNA interference, apoptosis, HeLa S3 cell