Abstract: Objective 　To study effect s of nimesulide in inducing apoptosis and suppressing expression of cyclooxygenase-2(COX-2) in human bladder cancer cell line T24. Methods 　Human bladder cancer cell line T24 cells were studied and human gast ric cancer cell line SGC-7901 was served as positive cont rol cell line. Cells were cultured for 24 hours with nimesulide at different concent rations. Apoptosis was detected by DNA fragmentation electrophoresis, while COX-2 by Western blot . Image Tool software was used to analyze Western blot image. Results 　With increase of nimesulide concent rations, cell apoptosis increased. COX-2 expression could be obviously suppressed by COX-2 specific inhibitor nimesulide. The concent ration of maximum suppressing effect was 100μmol/ L. Sof tware analysis revealed that with the increase nimesulide concent rations, and the expression of COX-2 obviously decreased. Difference was significant ( P < 0. 01) . Conclusion Nimesulide could effectively induced apoptosis in T24 cell line, which may be related to the expression inhibition of COX-2.