Abstract: Objective To investigate the therapeutical effect of cyclooxygenase-2 selective inhibitor Celecoxib on human endometrium adenocarcinoma and its mechanism. Methods Human endometrium adenocarcinoma xenografts were established in nude mice. When the diameter of tumor was about 5mm, the mice were divided into three groups randomely, which were treated with normal sodium, celecoxib of low dose (4mg/d) and celecoxib of high dose (2mg/d) respectively for two weeks. The size of the tumors were calculated every 3 days and tumor growth curve was depicted. At the end of the treatments，the mice were killed and the tumors were harvested. The tumor inhibition rate was calculated. The expression of COX-2 mRNA in tumor samples was detected by RT-PCR, and the expression of COX-2 protein and microvessel density were examined by immunohistochemistry. Results There was significantly inhibitory effect of celecoxib on xenografts in nude mice, and the tumor inhibition rates was upgraded (32.4% and 48.6% respectively) with the increase of celecoxib doses. RT-PCR results indicated that the expression of COX-2 mRNA was gradually decreased with the increase of celecoxib doses. Immunohistochemistry results revealed that the expression of COX-2 protein and microvessel density in tumor samples were gradually decreased with the increase of celecoxib doses. The differences between expreimental and control groups, as well as between two experimental groups were statistically significant（P<0.05）.The expression of COX-2 protein had positive correlation with microvessel density (r=0.921，P<0.01). Conclusion Celecoxib can inhibit the growth of human endometrium adenocarcinoma xenografts in nude mice. The mechanism may be associated with down-regulation of COX-2 expression and the decrease of microvessel density in tumor tissue.