The current study was conducted to explore the inhibitory effects of a small interfering RNA (siRNA) on3-phosphoinositide-dependent protein kinase 1 (PDK1) expression in esophageal cancer 9706 (EC9706) cells andthe influence on their biological behavior. After transfection of a synthesized PDK1 siRNA, PDK1 mRNA andprotein expression and the phosphorylation level of the downstream Akt protein were assessed using RT-PCRand Western blot analysis. Proliferation, apoptosis, cell invasion and in vivo tumor formation capacity werealso investigated using MTT, flow cytometry, Transwell invasion trials, and nude mouse tumor transplantion,respectively. PDK1 siRNA effectively suppressed PDK1 mRNA and protein expression, and down-regulated thephosphorylation level of the Akt protein in the EC9706 cells (P < 0.05). It also inhibited cell proliferation andinvasion, and promoted apoptosis; such effects were particularly obvious at 48 h and 72 h after transfection (P< 0.05). Growth of transplanted tumors was inhibited in nude mice, with decreased PDK1 expression in tumortissues. PDK1 may be closely correlated with proliferation, apoptosis and invasion of esophageal cancer cellsand thus may serve as an effective target for gene therapy.