Abstract： Objective To establish a stable orthotopic transplantation nude mouse model of the human pancreatic cancer and to explore the role of monitoring tumor growth with noninvesive MRI.Methods The tumors cells suspension made by the subcutaneous injection of human pancreatic cancer cell lines PANC1 were used as the source of tissue for orthotopic implantation of tissue.and transplanted into the pancreas of 20 BALB/C-nu nude mice.After implantation,the successful rate,tumor formation time,tumor growth speed,tumor shape and the change of signal of the tumor were monitored and recorded noninvasively by MRI.At the end of the 7th week,all the specimens were examined by pathological methods.Results Thirty-five percent (7/20)mice with implantation of primary human PANC1 adenocarcinoma cells were detected to have orthotopic implanted tumors by MRI after 15 days,and all the 20 nude mice developed pancreatic tumor within 27 days after operations,and the successful rate was 100%.Compared with adjacent normal tissue,the T1 WI imaging of 90%(18/20)of all the tumors showed uniformly hypo-intense signal,10%(2/20)showed iso-intense signal,the T2W 75%(15/20)showed uniformly hyper-intense signal.The tumor size 2,3,4,5,6,7 weeks after implantation was(912.6±2.4)mm3,(94.3±11.2)mm3,(175.9±82.5)mm3,(395.8±126.6)mm3,(1290.2±167.2)mm3,(1583.4±87.4)mm3,respectively.Pathologic examination confirmed poody differentiated pancreatic adenocatcinoma and it remained the primary tumor's biolosic features.Conclusions The orthotopic transplantation nude mouse model was in accordance with the feature of human pancreatic cancer and was easy for noninvasive monitoring,which provided an effective and stable in vivo experimental system.