Objective To construct RNAi combinant adenoviral expressive vectors specific to p65 subunit of NF-?B and to observe their gene silencing effect on p65 subunit.Methods Three pairs of complementary. single-strand DNA oligos targeting three various sites of p65 mRNA were designed and synthesized.Annealling was used to generate double-strand oligos(ds-oligos),and then the ds-oligos were cloned into pENTR~TM/u6 to generate the entry clone named pENTR.Recombination reaction in vitro with the pENTR and pAd/BLOCK-iT~TM- DEST was used to creat the adenovirus plasmid which contains the RNAi cassette.Then,the adenovirus plasmids digested with PacI were transfected into HEK293A cells to product adenovirus,and latter infected the HEK293A cells to amplify the adenoviral stock.Plaque forming assay was used to titer the adenoviral stock.The p65 gene silencing effect induced by the RNAi adenovirus was detected by Western blot and immunocytochemistry assay in ECV304 cells.Results The RNAi adenovirus specific to p65 subunit of NF-?B were produced with titer of 3.0 x 10~9pfu/ml to 2.5?10~10pfu/ml.The expression of p65 protein in ECV304 cells could be down-regulated efficiently by the RNAi adenovirus 48-72 h after infection,which would last for more than 6 days after infection.Conclusion RNAi adenovirus is an important tool inhibiting the expression of target gene efficiently.