Objective: To evaluate the effect of magnetic nanoparticle containing 5-fluorouracil (5-FU) targeting in treating chol- angiocarcinoma based on internal magnetic fields built inside the tumor. Methods: 32 nude mice of BABL/C bearing ectopic tumor were built by subcutaneouly injecting cholangiocarcinoma cell line QBC 939. Three weeks after tumor inoculation, the animal models were divided equally into four groups at random including: (a) group A, consisting of internal magnetic field built by magnetic biliary stent wires inserted into tumor tissue and receiving magnetic nanoparticles containing 5-FU administered via tail vein injection at 250 mg/kg for consecutive five days; (b) group B, receiving placebo (sodium chloride); (c) group C, receiving pure magnetic biliary stent wires without the applying of magnetic nanoparticles; (d) group D, consisting of external magnetic fields and the same treatment of magnetic nanoparticles containing 5-FU as group A. The tumor volumes were measured every 3 days, totally six times from treatment started. Tumor tissues were observed by transmission electron microscope when the nude mice were killed after the observation period. Results: The experimental group (group A) showed significantly therapeutic efficacy. Moreover, apoptosis of tumor cells could be easily detected in this group. Conclusion: Magnetic particles containing 5-FU combined with internal magnetic field can effectively treat cholangiocarcinoma, and its therapeutic efficacy is better than that of the traditional method based on external magnetic fields. Objective: To evaluate the effect of magnetic nanoparticle containing 5-fluorouracil (5-FU) targeting in treating chol- angiocarcinoma based on internal magnetic fields built in the tumor. Methods: 32 nude mice of BABL / C bearing ectopic tumors were built by subcutaneouly Three weeks after tumor inoculation, the animal models were divided equally into four groups at random including: (a) group A, consisting of internal magnetic field built by magnetic biliary stent wires inserted into tumor tissue and receiving magnetic nanoparticles containing 5-FU administered via tail vein injection at 250 mg / kg for consecutive five days; (b) group B, receiving placebo (sodium chloride); (c) group C, receiving pure magnetic biliary stent wires without applying magnetic nanoparticles; (d) group D, consisting of external magnetic fields and the same treatment of magnetic nanoparticles containing 5-FU as group A. The tumor volumes were measured e very 3 days, totally six times from treatment started. Tumor tissues were observed by transmission electron microscope when the nude mice were killed after the observation period. Conclusion: Magnetic particles containing 5-FU combined with internal magnetic field can effectively treat cholangiocarcinoma, and its therapeutic efficacy is better than that of the traditional method based on external magnetic fields.