Abstract: Objective :To investigate the effect of Triptolide on the growth of human pancreatic cancer cell by regulating the protein expression of 5-lipoxygenase (5-LOX). Methods : Pancreatic cancer cell lines SW 1990 and Capan2 were used in this study. SP immunocytochemical staining was used to detect the protein expression of 5-LOX in the pancreatic cells SW1990 and Capan2. The effect of Triptolide (TL) on pancreatic cancer cell line SW1990 was determined by SP immunocyt chemical staining, MTT and flow cytometry (FCM). Results : The protein expression of 5-LOX in pancreatic cancer cell lines SW1990 and Capan2 were demonstrated by immunocytochemical staining. Staining for the5-LOX protein was more evident in the well differentiated pancreatic cancer cell line Capan2 than the moderately differentiated pancreatic cell line SW1990. This study also demonstrated that the proteinexpression of 5-LOX was inhibited by TL. The cell proliferation was blocked by TL, which showed a significant positive association with the level of TL concentration (P<0.01). The FCM analysis showedthat the prc)-apoptotic effect of TL on cell line SW1990 was in a concentration-Dependent manner. There was correlation between the expression of 5 -LOX and proliferation or apoptosis index in ourstudy (P<0.01). Conclusions :TL can inhibit the proliferation and induce apoptosis of pancreatic cancer cells by regulating the expression of 5-LOX protein.