The invention discloses a magnetic graphene and polyaniline nano-composite and a preparation method and application thereof and belongs to the technical field of composites. According to the magnetic graphene and polyaniline nano-composite, alcohol containing 1-5 carbon atoms serves as a solvent, a graphene/polyaniline composite, FeCl3 and sodium acetate are dissolved in the solvent, the mixture is ultrasonically treated, then the mixture reacts in a high-pressure reactor, and then the magnetic graphene and polyaniline nano-composite can be obtained. The composite prepared through the method overcomes the defects that graphene slice layers are prone to be stacked and pure polyaniline is prone to be agglomerated. The adsorbent is used for adsorbing phenolic estrogen in water, and the adsorption performance superior to that of a magnetic graphene material and that of a magnetic polyaniline material is shown. The adsorption efficiency for the phenolic estrogen is improved through graphene modified by a magnetic material and polyaniline, and meanwhile separation is quite easy due to magnetism of the material. The magnetic graphene and polyaniline nano-composite has the advantages of being efficient in adsorption and easy to operate.