In view of gemcitabine resistance has limited clinical activity of gemcitabine as a cellulotoxic drug in pancreatic cancer patients, this study is designed to investigate the effect of emodin on the sensitivity of pancreatic cancer to gemcitabine as well as its mechanism. After gemcitabine-resistant pancreatic cancer cell line (SW1990/GZ) was established by escalating doses of gemcitabine serially in pancreatic cancer cell line (SW1990). The cellular proliferation was detected by cell counting kit-8 (CCK-8) assay. Flow cytometry (FCM) was used to determine apoptosis of pancreatic cancer cells. The activity of NF-kappaB in pancreatic cancer cells was measured by electrophoretic mobility shift assay (EMSA). Western blotting was used to detect the protein expression of Bcl-2 and Survivin in SW1990/GZ cells. Metastatic model simulating human pancreatic cancer was established by orthotopic implantation of histologically intact human tumor tissue into pancreatic wall of nude mice. Also, immunohistochemistry was used to detect the positive expression of Ki-67, NF-kappaB, Bcl-2 and Survivin in the tumors. The results show that pretreatment of cells with emodin followed by gemcitabine induced a higher percentage of growth inhibition and apoptosis of pancreatic cancer cells than that of gemcitabine alone. In addition to in vitro results, emodin in combination with gemcitabine is much more effective as an antitumor agent compared to either agent alone in the orthotopic tumor model. Further study showed that the emodin with or without gemcitabine significantly down-regulates NF-kappaB and its regulated molecules such as Bcl-2 and Survivin proteins both in vitro and in vivo. It is concluded that inactivation of NF-kappaB signaling pathway by emodin resulting in the chemosensitization of pancreatic cancer to gemcitabine, which is likely to be an important and novel strategy for the treatment of pancreatic cancer.