A kind of superparamagnetic microsphere and preparation method thereof, under the condition of vacuum or nitrogen protection and room temperature, soak porous or hollow microsphere in metal ion solution, rotary evaporation, add ammonia water or sodium hydroxide solution, stir reaction, magnetic field Isolate porous or hollow magnetic microspheres, wash them with alcohol, add surfactant, isopropanol, ammonia water and ethyl orthosilicate to obtain superparamagnetic microspheres coated with silicon dioxide, which can also be used on the surface of microspheres Selectively assemble various functional groups. The inner pores of the microspheres have good compatibility with metal ions, the magnetic nanoparticles are evenly distributed, have good superparamagnetism, chemical and physical stability, acid and alkali resistance, and are not easy to oxidize or agglomerate. The process is simple, less equipment is required, the control is convenient, the output rate is high, the production cost is low, and it is easy to organize mass production.