Abstract: Objective :To investigate the effect of valdecoxib,a selective COX-2 inhibitor,on apoptosis and expression of the COX-2 of human Eca109 cell line. Methods :MTT assay and flow cytometry were used to observe the effect of valdecoxib on proliferation,apoptosis and the cell cycle distribution of Eca109 cells.Transmission electron microscope was used to further detect the apoptosis.RT-PCR was used to detect the mRNA expression of COX-2;the expression of COX-2 protein was detected by flow cytometry. Results :Valdecoxib in 25~400(mol.L-1 significantly inhibited the proliferation of Eca109 cell line in a time-and dose-dependent way,the inhibition rate of proliferation was 23.09～85.95% after 72h,and the rate of apoptosis was increased from(2.38±0.42)% to(2.95±0.83)%～(48.46±0.73)%,50～400mol.L-1 valdecoxib also decreased the proliferation index and the proportion of cells in the S phase,increased the proportion of cells in the G0/G1 phase,but had no effect on the proportion of cells in the G2/M phase.Compared with those in Eca109 cells cultured in the medium with solvent,both mRNA and protein level was decreased in the Eca109 cells exposed to valdecoxib in a dose-dependent way in 72h. Conclusion :Valdecoxib could effectively induce apoptosis in the Eca109 cell line,which may be related to inhibiting the expression of COX-2.