Abstract: Objective：To investigate the blockage of constitutively activated signal transducers and activators of transcription3(Stat3) signal and the effect on cell apoptosis by applying RNA interfere technique to silence Stat3 gene in human esophageal squamous cell carcinoma cell line(EC9706). Methods：EC9706 was transfected with chemical syntheswased Stat3 siRNA（100nM），RT-PCR and Western blotting were used to detect the expression of Stat3 mRNA, the protein levels of Bcl-2,Stat3 and phosphorylated-Stat3(p-Stat3) before and after transfection. The change of DNA-binding activity and the cells apoptosis were evaluated by electrophoretic mobility gel shift assay (EMSA) and FCM, respectively. Results：After transfected Stat3 siRNA 48h, cells morphology were significantly transformed.RT-PCR and Western blot showed the expression of Stat3 gene was inhibited at mRNA and protein levels by Stat3 SiRNA and the constitutively activated Stat3 signal was blocked. Stat3-DNA-binding activity was supresssed directly at DNA level comfirmed by EMSA. The expression of Bcl-2 protein was reduced after transfected by Stat3 siRNA.FCM indicated cell that apoptosis was promoted significantly in EC9706. Conclusion：Stat3 siRNA blocked the constitutively actived Stat3 signaling specially and efficiently in EC9706, which promoted cell apoptosis obviously.