The invention provides magnetic iron and manganese oxide synthesized by aerobic microorganisms and application of the magnetic iron and manganese oxide. A synthesizing method of the magnetic iron and manganese oxide includes the steps of firstly, under an aerobic condition, manganese oxidizing microorganisms and iron reducing microorganisms in the a microorganism colony are coordinated to achieve a synergic effect to oxidize divalent manganese ions into manganite and partially reduce iron ions into ferrous ions to form magnetic Fe3O4; secondly, the material obtained in the first step is centrifuged, solid precipitate is collected, and vacuum drying and grinding are performed on the solid precipitate to obtain the magnetic iron and manganese oxide. The magnetic iron and manganese oxide which is prepared by using a pure natural microorganism method under normal temperature and normal pressure has a good adsorption effect on various heavy metals.