The invention relates to a preparation method of a magnetic metal ion surface molecular imprinted material. The method comprises the steps as follows: firstly, preparing a Fe3O4 magnetic material; then, hydrolyzing tetramethoxysilane and chitosan in an acetic acid solution to obtain a gel material, and wrapping the Fe3O4 magnetic material with the gel material to obtain a Fe3O4@SiO2 material; grafting the prepared Fe3O4@SiO2 material with a complex of iminodiacetic acid and zinc ions, conducting a polymerization reaction under the action of template molecules, a crosslinking agent and an initiator to form a polymer with a core-shell structure, and eluting the template molecules from the polymer to obtain the magnetic Fe3O4@SiO2-IDA-Zn<2+> surface molecular imprinted material. Intermolecular force and metal ion coordination exist between the template molecules and the imprinted material, the acting force is high, and the imprinted material can be applied to effective enrichment and detection of ractopamine in actual samples.