The work aims to study the effect of PVP on the dispersion of Fe3O4 on the surface of graphene to obtain the absorbing material with good absorbing properties. The graphene/Fe3O4 composite absorbing materials were prepared by solvothermal method. The graphene/Fe3O4 composite absorbing materials were characterized by scanning electron microscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy and vector network analyzer. Effects of PVP (dispersant) whether added or not on the morphology and absorbing properties of graphene/Fe3O4 composite absorbing materials were studied. On graphene/Fe3O4 composite absorbing materials added with PVP, the agglomeration of Fe3O4 significantly decreased and the size was significantly reduced, compared with that not added with PVP. Through the reflectivity simulated by computer, the maximum reflection loss of graphene/Fe3O4 composite absorbing materials without PVP reached -18.79 dB at 16.25 GHz at a matching thickness of d=2.00 mm and the frequency bandwidth of composite materials with reflection loss less than -10 dB could reach 4.1 GHz. The composite materials with PVP could reach the maximum reflection loss of -25.88 dB at 16.25 GHz when the matching thickness was d=2.00 mm, and the frequency bandwidth of the composite materials with the reflection loss less than -10 dB could reach 4.5 GHz. Compared with the composite absorbing materials without PVP, the frequency bandwidth of materials with reflection loss less than -10 dB increased by 0.4 GHz and the maximum reflection loss increased by 7.09 dB. PVP can improve the dispersion of Fe3O4 on the surface of graphene and form a good conductive network, and the microwave absorption performance is obviously improved.