The present invention discloses a magnetic nanocomposite for inhibiting/treating cancer and a method for fabricating the same. The magnetic nanocomposite comprises a core formed of a plurality of magnetic nanoparticles made of ferric ferrous oxide (Fe3O4) a shell made of a carboxy-functionalized polyaniline and an anti-tumor medicine bound to the external surface of the shell. The method of the present invention fast fabricates the magnetic nanocomposite in a simple way. The medicine of the present invention has a longer half life and a better thermal stability. The present invention disperses the water-insoluble medicine in water uniformly to decrease the biological rejection. Moreover, the magnetic nanocomposite of the present invention is guided to the nidus by an external magnetic field to increase the local concentration of the medicine and provide an effective chemotherapy. Therefore, the present invention has competitive advantage over the conventional BCNU.一種用於抑制/治療腫瘤之磁性奈米複合物及其製備方法,此磁性奈米複合物是以四氧化三鐵的磁性奈米粒子為核心,以羧基化聚苯胺高分子為殼層,並以抗癌藥物固定於殼層外部,不但製備方法簡單快速,並可使藥物半衰期延長及提高活性,且明顯改善抗癌藥物之熱穩定性與儲存安定性,能使不溶於水溶液的藥物均勻分散於水溶液中,降低生物體內之排斥副作用,再者,可藉由磁場導引於患部,增加局部藥物濃度,以達到集中治療的目的,因而極具商業競爭潛力。