Abstract: Objective: To investigate the efficacy and toxicity of magnetic adriamycin nanoparticles (MAG- ADM- NP) in vivo for targeted embolotherapy of hepatocellular carcinoma (HCC). Methods:MAG- ADM- NP were successfully constructed. The hepatocellular carcinoma model was established in rats and after 4 months, they were divided into 5 groups as follows: the MAG- ADM- NP group, the magnetic fluid group, the free Adriamycin group, the Lipiodol group and the control group. All of the animals underwent a midline abdominal incision. A cannula was inserted into the gastro- duodenal artery. The drugs were administered at 5 mg/ kg, equivalent to the dose of free adriamycin. All of the tumor tissues were exposed to the magnetic field for 30 min. After two weeks the tumors were excised and weighed, and the tumor- inhibiting rates were calculated. The tumor and heart tissue were examined by histology. The tumor tissues were also observed by transmission electron microscope. Results: The MAG- ADM- NP were round and smooth with a uniform size and a diameter of about 70 nm. The drug loading rate was 5.29% and encapsulation efficiency was 90.4%. After the drugs were administered, the tumor- inhibiting rates of the MAG- ADM- NP group, the magnetic fluids group, the free Adriamycin group and the Lipiodol group were 76.6%, 60.8%, 30.4% and 25.9%, respectively, compared to the control group. Small areas of necrosis were observed in the Lipiodol group and the free Adriamycin group. Larger areas of necrosis were observed in the magnetic fluids group. The necrosis areas seen in the MAG- ADM- NP group were the largest among the five groups. Conclusion: MAG- ADM- NP have been successfully constructed. The tumor- inhibiting rate of MAG- ADM- NP was higher than that of the other treatments tested. Pathological examination showed that MAG- ADM- NP could effectively kill carcinoma cells and they caused less toxicity than free Adriamycin.