The effect of targeted magneticnanoparticles on hepatoma and the underlying mechanism were examined. Nude mice transplanted with a humanhepatomacell line (HepG2 cells) were randomized into 5 groups, including (1) group A, receiving normal saline, (2) group B, receiving 5-fluorouracil (5-Fu), (3) group C, receiving magneticnanoparticles containing 5-Fu, (4) group D, consisting of treatment with magneticnanoparticles containing 5-Fu and inside magnetic field and (5) group E, receiving pure magneticnanoparticles and inside magnetic field. Morphological features of transplanted tumors in mice in each group were observed under transmissionelectron microscope (TEM). The expression of bcl-2/bax protein was immunohistochemically detected by SABC method. The results showed that a large number of apoptotic tumorcells were found in group B and group D under TEM. The expression of bcl-2 protein was significantly decreased and the expression of bax protein increased significantly in both group B and D as compared with those in group A, C and E (P<0.01 for all). The decrease in bcl-2 and the increase in bax were more in group D as compared with group B (P<0.01). It is concluded that the targeted magneticnanoparticles containing 5-Fu can improve the chemotherapeutic effect of 5-Fu by decreasing bcl-2 expression, increasing bax expression and inducing apoptosis of the liver cancercells.