Magnetic microsphere is a composite magnetic material with rich surface functional group. Porous starch was prepared by corn starch hydrolysis using biological enzymatic method

then 10—15 μm magnetic porous starch microspheres can be obtained by mixing Fe3O4 magnetic fluid and porous starch by multiple shake and centrifugation. Oval or spherical magnetic microspheres with rich hydroxyl and carboxyl functional groups can be observed by SEM and FTIR. The obtained magnetic microspheres can be uniformly distributed in aqueous solution and have strong magnetic response in an external magnetic field.