The invention discloses a 
magnetic composite nano 
microsphere capable of emitting 
fluorescent light and a preparation method thereof, which belong to the inorganic nanophase material field. The preparation method comprises the following steps: firstly, the 
sol-
gel method or the reversed phase 
microemulsion method is adopted for performing base 
catalysis on 
alkyl silicate, and a layer of 
silicon dioxide is uniformly coated on the surface of inorganic magnetic nano particles; secondly, an amino 
silane coupling agent is adopted for performing 
surface finish on 
silicone dioxide; thirdly, 
semiconductor quantum dots are absorbed on the surface of the 
silicone dioxide through the electrostatic action between an amino group and a carboxyl group on the surface of the amino 
silane coupling agent; and fourthly, the 
magnetic composite nano 
microsphere with a core-shell structure capable of emitting the 
fluorescent light is obtained. The preparation method has easy obtained raw materials and low cost. The composite nano 
microsphere obtained has good stability, controllable grain size, narrow distribution, and has good magnetic 
responsivity and performance of being capable of emitting the 
fluorescent light, and the two performances are controllable. The 
magnetic composite nano microsphere and the preparation method can be applied in the fields of 
biomedicine, bioengineering, etc. including 
immunoassay, biological labeling and separation, 
cell imaging and so on.