Abstract: Objective: To construct a small interfering RNA (siRNA) expression vector targeting the signal transduc-ers and activators of transcription 3 (Stat3) gene and to investigate the impact and mechanism of a blockade of the stat3signaling pathway in the SGC7901 cell line. Methods: After successful construction of a Stat3siRNA expression vector, itwas transfected into SGC7901. RTPCR, Western blot, MTT and flow cytometry were used to detect the mRNA expres-sion, the protein expression, cell proliferation and apoptosis. Results: A Stat3siRNA expression vector was successfullyconstructed. The results of Western blot and RTPCR showed that the expression of Stat3 decreased significantly (P<0.05),especially under the influence of siRNA3. MTT showed that cell proliferation was significantly reduced after transfection ofthe siRNA vector into SGC7901 cells. Flow cytometry results suggested that more apoptosis was seen in the siRNA group(P<0.05). Conclusion: RNAi of Stat3 can effectively inhibit Stat3 expression, suppress the proliferation of cancer cells,and promote apoptosis.