The purpose of this work was to construct the plasmid that could direct the synthesis of siRNA-like transcripts and thus mediate strong and specific repression of human heat shock protein 90β(Hsp90β)gene expression and to compare the transfection efficiency of the plasmids in varying conditions of transfection.Three 64 nt oligos corresponding to different regions of the target gene were chemically synthesized and annealed and were then ligated with pSUPER EGFP1 plasmid and double-digested with HindⅢ and BglⅡ.Recombinant plasmids were transformed into Escherichia coli,DH5a,and the colonies were picked and grown in the Amp-agarose.The presence of positive clones was checked by the means of endodigestion and sequencing.Three cell strains,HepG2,Human umbilicus vein endothelium cells(HUVEC) and HeK293,were cultured.Then the plasmids were transfected into the cells at difierent ratios of plasmid to Lipofectamine.The transfection efficiency was measured by detection of enhanced green fluorescence protein (EGFP).The presence of positive recombinant clones were verified by double-digestion and sequencing.The bases inserted into the plasmids were correct and the positive colonies were named pSuper-Hsp90β1,pSuper-Hsp90β2 and pSuper-Hsp90β3.After optimizing the ratio of plasmid to Lipofectamine,we achieved high transfection efficiency in HeK293 cells.Transfection efficiency was still low in the HepG2 cells.In conelusion,the si-RNA-synthesizing plasmids targeting Hsp90β were constructed and transfected into cells with different transfection efficiency.