Abstract： Objective To study inhibitory effects of transcription factor activator protein-2α(AP-2α)on proliferation of colon cancer cells in vitro and its mechanism. Methods The peDNA3.1 (+)-AP-2α recombinant plasmid was constructed. Plasmid pcDNA3.1(+)- AP-2α and pcDNA3.1(+)was transfected into SW620 cell by liposome mediation for transient expression, and proliferative activities of SW620 cell were evaluated by MTT assay. The change in the mRNA and protein expression level of ER-β before and after transfection was detected using the methods of Real-Time PCR and Western blotting respectively. Results The mRNA and protein expressions of AP-2α could be enhanced by transfecting of AP-2α gene in SW620 cell. MTT assay indicated: the proliferation velocity of SW620 cell for transfection of the pcDNA3.1(+)-AP-2α plasmid was apparently inhibited. The expression of ER-β in SW620 cell increased significantly after AP-2α gene transfection. Compared with control group, the difference was significant (P＜0.05). Conclusion Overexpression of AP-2α inhibits the proliferation of SW620 cell in vitro, which is probably related with activation of ER-β.