Abstract: Superparamagnetic iron oxide nanoparticles（SPIONs） were synthesized by thermal decomposition of iron（Ⅲ） acetylacetonate（Fe（acac）₃） in polyethylene glycol（PEG）, which was used as solvent,reducing and modifying agent. TEM images showed that the average size of the crystal grains was 7.5±1.0 nm. The crystal grains were in regular shape and well dispersed. The XRD result showed that the SPIONs were well crystallized Fe₃O₄. Maleic anhydride（Mal） was conjugated with the PEG on SPIONs,and then to form chemical bonds with angiopep-2（ ANG） or transferrin（Tf） by EDC-NHS method. The hydrodynamic size and zeta potential of ANG/Mal/PEG/-SPIONs were 42 nm,-9.86 mV, respectively.The modification content of ANG was 19 wt%, and the saturation magnetization was 58 emu/g; The hydrodynamic size and zeta potential of Tf/Mal/PEG/-SPIONs were 96 nm, 2.29 mV, respectively. The modification content of ANG was 10 wt%, and the saturation magnetization was 43 emu/g. The SPIONs modified with biomolecules Tf and ANG have great potential in biomedical application.