Objective To investigate the activity of cyclooxygenase-2 (COX-2) gene promoter of human gastric cancer cells under inflammatory state. Methods The expression of COX-2 in human gastric cancer tissues was detected with immunohistochemical staining. Recombinant pGL3-COX-2-promoter of human COX-2 gene promoter was constructed, and gastric cancer cell line SGC-7901 and BGC-823 were co-transfected with pGL3-COX-2-promoter and pRL-TK with lipofectin reagent-mediated transfection. Cells were collected after treatment with different mass concentrations of lipopolysaccharide (LPS) for different time, the activity of dual-luciferase reporter gene was determined with dualluciferase reporter system, and the expression of COX-2 protein was detected by Western blotting. Results Immunohistochemical staining indicated that COX-2 protein expressed both in cytoplasm of gastric cancer cells and cytoplasm of para-cancer mucosal epithelial cells. At the same time point, the activity of COX-2 gene promoter of SGC-7901 cells and BGC-823 cells increased with the mass concentrations of LPS （P<0.05）. The activity of COX-2 gene promoter reached the peak after treatment with high concentration of LPS (10 μg/mL) for 6 h, and then gradually decreased (P<0.05). Western blotting revealed that the expression of COX-2 protein of SGC-7901 cells and BGC-823 cells increased with the time of treatment with 10 μg/mL LPS. Conclusion Inflammatory stimulation may activate COX-2 gene promoter of human gastric cancer cells.