Abstract: In order to improve the dispersion degree of graphene oxide (GO)/Fe₃O₄ composites, modified graphene oxide (GOP) was obtained by functional modification of GO surface with triphenylphosphine (PPh3). GOP/Fe₃O₄ composites was synthesized in one step by coprecipitation method. The morphologies, structures and magnetic properties of GOP/Fe₃O₄ composites were characterized by SEM, TEM, XRD, FTIR, Raman and VSM. The electromagnetic parameters of the GOP/Fe₃O₄ composites were measured by phasor network analyzer (PNA), and the electromagnetic wave absorption properties of GOP/Fe₃O₄ composites were simulated. The results show that the maximum absorption peak value of GOP/Fe₃O₄ composites is -25.4 dB and the maximum absorption bandwidth is 6.0 GHz, which is greatly improved compared with the unmodified GO/Fe₃O₄ composites.