AIM: To investigate the anti-tumor effect and mechanisms of magnetic nanoparticles targeting hepatocellular carcinoma.METHODS: Human hepatocellular carcinoma was induced in nude mice, and the mice were randomly divided into group A receiving normal saline, group B receiving magnetic nanoparticles containing 5-fluorouracil(5-FU), group C receiving 5-FU, and group D receiving magnetic nanoparticles containing 5-FU with a magnetic field built in tumor tissues. The tumor volume was measured on the day before treatment and 1, 4, 7, 10 and 13 d after treatment. Tumor tissues were isolated for examination of the expression of bcl-2, bax and caspase 3 by immunohistochemical method, reverse transcription polymerase chain reaction and Western blotting.RESULTS: The tumor volume was markedly lower in groups C and D than in groups A and B (group C or D vs group A or B, P＜0.01). The volume was markedly lower in group D than in group C (P＜0.05). The expression of protein and mRNA of bcl-2 was markedly lower in groups C and D than in groups A and B (group C or D vs group A or B, P＜0.01), and was markedly lower in group D than in group C (P＜0.01). The expression of bax and caspase 3 in groups C and D was significantly increased,compared with that in groups A and B (P＜0.01).CONCLUSION: The targeted magnetic nanoparticles containing 5-FU can improve the chemotherapeutic effect of 5-FU against hepatocellular carcinoma by decreasing the expression of bcl-2 gene, and increasing the expression of bax and caspase 3 genes.