Abstract: Objective This study was to detect whether curcumin inhibits NF-κB signaling pathway through suppression IκBα phosphorylation and evaluate the effects on proliferation and cell cycle in EC9706 and Eca109 cell lines. Methods ESCC cells were treated with different concentrations of curcumin and then the number of viable cells were determined by MTT. Cytoplasmic extracts or whole cell extracts were examined for the expression of pIκBα and cyclinD1 using Western Blotting after treated with curcumin at different time. ESCC cells were treated with curcumin, 5-FU or combinations thereof for 72h. The cells were stained with PI and analyzed cell cycle by flow cytometry. Results The results showed that curcumin inhibited two ESCC cells growth in a concentration-dependent manner. The Western blotting results indicated that curcumin inhibited IκBα phosphorylation and downregulated the expression of cyclinD1 in the two ESCC cell lines in a time-dependent manner. CyclinD1 was declined in the forepart of curcumin-treated cells. Curcumin-treated cells showed an increase in the percentage of cells in the G0/G1 phase and a decrease in the percentage of cells in the S phase. While combination with 5-FU, the results were more prominence. Conclusion Therefore, curcumin inhibits the phosphorylation of IκBα and downregulates the activation of NF-κB signaling pathway, leading to suppression of proliferation in ESCC cell. Therefore, curcumin may prove useful in the treatment of ESCC because it is a pharmacologically safe compound without side effects.