Firstly, it has gotten aminization of KH550 modified Fe3O4 nanoparticles, then using it as stabilizer, using toluene as soft template, made Pickering emulsion with aniline . Finally, the electromagnetic composites of PANI/Fe3O4 were prepared by interfacial polymerization method with presence of ammonium sulfate (APS) (as oxidant), hydrochloric acid (HCl) (as dopant). The structural properities of Fe3O4 nanoparticles and composites were characterized by FTIR, SEM, XRD, effects of different concentration of dopant HCl on the composites were inspected by vibration sample magnetism(VSM). The results show that the concentration of hydrochloric acid is 0.1 mol/L, the magnetic saturation intensity of composites reached 24841 A/m. Electromagnetic shielding performance and absorbing properties of composites were analyzed by vector network analyzer (VNA). The results show that the shielding effectiveness of composites were 40.682 dB at frequency of the electromagnetic wave was 10160 Hz, reflection loss reached -47.043 dB at 12400Hz, when HCl concentration is 0.1 mol/L, thickness 1 mm.