We have developed a drug-loaded, pH-sensitive, nano-magnetic targeted system (DPNTS) for delivering doxorubicin (DOX) to tumor tissues through a facile route. Iron oxide (Fe3O4) nanoparticles were used as magnetically-responsive carriers, polyethyleneglycol (PEG) as the surface-modifying agent, and polyethyleneimine (PEI) as the drug-loading site whose primary amine reacts with the 13-carbonyl of DOX. The prepared DPNTS was within 20 nm and had good stability in dispersion and superparamagnetic properties. DOX was grafted to PEG/PEI@Fe3O4 at up to 85 %. During in vitro release studies, nearly 81 % DOX was released from DPNTS within 72 h at pH 4.5, compared with only 28 % at pH 7.4.