This project was carried out in three stages. In the first stage, Fe3O4 nanoparticles were prepared by co-precipitation method utilities using NH3 solution. The crystal structures and morphology of nanoparticles were investigated and characterized by X–ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. In the second part, Conducting polyaniline/nanoparticles (TiO2 and Fe3O4) composites were synthesized by in situ polymerization method with ammonium persulfate (APS) as the oxidant and under an ice-water bath (0 oC). In last step, nanocomposite powders were completely dispersing in paraffin and were followed by casting process on test plate. The radar absorbing property of nanocomposite was investigated by vector network analyzer at the frequency range of 8-12 GHz. The best absorption was caused by the nanocomposite when the concentration was about 10% and thickness of 4 mm. Maximum reflections recorded about -33.26 dB and around 9.5GHz.