In the present study, superparamagnetic maltotrionic acid-coated magnetite nanoparticles (MAM) were surface modified with doxorubicin (DOX) and RGD peptide to improve their intracellular uptake, ability to target tumor cells and antitumer effect. RGD was added to the distal end of MAM aiming to construct an enhanced tumor targeting delivery system. To test its targeting effect, DOX, a widely used anticancer drug, was immobilized on the RGD-modified magnetite nanoparticles. DOX-coated magnetite nanoparticles were also prepared as a control. KB cell culture experiment showed that both DOX-modified nanoparticles and DOX-RGD peptide-modified magnetite nanoparticles (DRMAM) were internalized into the cells. But the uptake amount of DRMAMs was higher than that of DOX-modified nanoparticles. This result indicates that DRMAMs have a great potential to be used as contrast agent and antitumor medicine.