Abstract: Objective 　Signal t ransducer and activator of transcription 3 (Stat3) is activated in response to cytokines and growth factors stimulation, and activation of Stat3 is involved in modulating cell proliferation, differentiation and apoptosis. The purpose of the study was to examine colon cancer cell lines to determine whether Stat3 plays an important role in the process of apoptosis in colon cancer cells. Methods 　Protein lysates were ext racted from colon cancer cells. Human colon cancer cell line HCT116 was t ransfected with Stat3 antisense oligonucleotide mediated by liposome, MTT assay was used to measure the proliferation, flow cytometry was applied to analyze the cell cycle and apoptosis, the expression of Stat3, p-Stat3, bcl-2, bcl-xL, Mcl-1 and Caspase-3 were measured by western blot . Results 　Targeting of Stat3 using antisense oligonucleotide directed against the t ranslation site, resulted in apoptosis and downregulation of Stat3, p-Stat3 and bcl-2 family members. Conclusion 　Constitutive activation of Stat3 is associated with the carcinogenesis of colon cancer cells. Blocking of Stat3 signaling could induce apoptosis of colon cancer cells.