Objective To investigate the effect of a selective cyclooxygenase-2 inhibitor on tumor metastasis,tumor angiogenesis,and vascular endothelial growth factor(VEGF)of orthotopic implanted human gastric carcinoma in non.obesity diabetes(NOD)severe combined immune deficiency(SCID)mice.Methods Human gastric cancer SGC-7901 tissues were orthotopically implanted into the stomach of the NOD SCID mice.Forty mice were randomly divided into two groups which received either intravenous injections of 0.9% Nacl solution (0.9% NaCL solution group)or 50mg/kg.d Nimesulide(Nimesulide group)twice weekly for two weeks.Mice were sacrificed in the 5th week after implantation.Tissues from stomach and other organs were obtained for histopathologieal evaluation.The intratumoral microvessel density(MVD)and VEGF protein expression in tumor were evaluated by immunochemical method.Results The tumor metastasis rates were 18/20 in 0.9% Nacl solution group and 5/20 in Nimesulide group(P＜0.05).MVD was 9.5±2.9 in 0.9% NaCl solution group and 3.9±2.1 in Nimesulide group(P＜0.01).VEGF protein expression was 90% in 0.9%NaCl solution group and 25% in Nimesulide group(P＜0.01).Conclusions Nimesulide can inhibit the metastasis or gastric cancer through inhibiting tumor VEGF expression and tumor angiogenesis with no obvious anticoagulant activity.