In　this　paper,　the　magnetite/polyaniline　(PANI)　nanocomposite　was　prepared　by　the　novel　reverse　in　situ　polymerization　method.　Fe3O4　magnetic　nanoparticles　were　synthesized　in　situ　in　PANI　chloroform　solution　to　form　a　suspension　containing　the　Fe3O4/PANI　nanocomposite.　It　overcame　the　disadvantage　of　oxidation　of　the　Fe3O4　by　the　oxidant　in　conventional　method.　The　Fe3O4/PANI　chloroform　suspension　and　the　Fe3O4/PANI　powder　were　characterized　by　FT-IR,　TEM,　XRD,　vibrating　sample　magnetometer,　Gouy　magnetic　balance,　conductivity　meter,　and　vector　network　analyzer.　It　is　demonstrated　that　the　Fe3O4/PANI　suspension　has　a　good　electrical　conductivity　that　is　up　to　2.135　mu　S/cm　at　the　optimal　ratio　of　reactants.　The　Fe3O4　nanoparticles　are　well　dispersed　in　the　PANI　network　with　a　particle　size　of　about　10　nm.　Fe3O4/PANI　powder　has　high　saturation　magnetization　and　magnetic　susceptibility,　as　well　as　a　broad　application　prospect　in　the　field　of　electromagnetic　devices.　The　Fe3O4/PANI　powder　exhibits　an　excellent　microwave　absorption　behavior,　which　can　be　an　outstanding　candidate　for　the　rapid　development　of　broadband　shielding　materials.