The invention discloses a porous magnetic 
starch microsphere and a preparation method thereof. The method is characterized in that 
organic peroxide-
surface modified Fe3O4 magnetic particle is used as a 
nucleus, 
mineral oil is used as a continuous phase, 
starch molecules and the magnetic 
nucleus are combined through reversed-phase 
polymerization reaction to form a magnetic 
starch micro 
sol particle with a nuclear-shell structure, the starch molecules on a shell layer are subjected to cross-linking reaction under the action of cross-linking agent-
epoxy chloropropane, so that the magnetic starch micro 
sol is gelatinized to obtain magnetic starch micro gel, then the magnetic starch micro gel is subjected to demulsification, washing, 
magnetic separation, supercritical CO2 extraction and 
drying to obtain the porous magnetic 
starch microspheres. The porous magnetic starch 
microsphere is round, has uniform particle size, narrow pore size distribution, large specific surface and high 
mechanical strength, and the porous magnetic starch has a magnetic guiding function and a flexible and strong adsorption loading function, and has wide application prospect in the fields of 
sewage treatment, targeted drugs, catalytic industry, environment monitoring, immobilized enzymes and the like.